This was CNBC's live blog tracking developments on the war in Ukraine.

Russia warned Monday that the risk of a "direct military clash" between Russia and nuclear powers in the West is rising.

"Westerners are dangerously balancing on the brink of a direct military clash between nuclear powers, which is fraught with catastrophic consequences," Russian Foreign Minister Sergey Lavrov said in a video message to the participants of the Moscow Nonproliferation Conference.

The comments come after Russia reacted angrily to the U.S. House of Representatives passing a $61 billion foreign aid package for Kyiv at the weekend.

House lawmakers approved the aid Saturday despite long-standing objections from hardline Republicans; the bill now passes to the Democratic-majority Senate, which is expected to approve the legislation later this week before it's passed to President Joe Biden to sign it into law.

The aid is a lifeline for Ukraine, whose forces in the east of the country have had to ration their usage of shells amid shortages of supplies; Russian forces have been making gains in the Donbas region, with Ukraine pleading for more air defense systems, artillery and ammunition to turn the tide in the war.

Ukrainian President Volodymyr Zelenskyy thanked U.S. lawmakers saying the bill passed by the House "will keep the war from expanding, save thousands and thousands of lives, and help both of our nations to become stronger." He urged the Senate to pass the bill as quickly as possible.

Russia hits TV infrastructure in Ukraine's Kharkiv, signal disrupted

A Russian air attack on Ukraine's second biggest city, Kharkiv, hit TV broadcast infrastructure, prompting disruptions with the signal, a local official said.

"At the moment, there are interruptions in the digital TV signal," regional governor Oleh Syniehubov said.

There were no casualties, he added.

— Reuters

EU ministers stop short of Patriot pledges for Ukraine

European ministers said on Monday they were looking urgently at how to provide more air defence to Ukraine but they stopped short of concrete pledges of the Patriot systems that Kyiv values most.

Meeting in Luxembourg, foreign and defence ministers from the European Union said the U.S. House of Representatives vote to approve a $60 billion Ukraine package at the weekend should not lead to any complacency on their part.

"We can be joyous for a day but we have to be prepared for the battle that is coming tomorrow. Therefore there can be no calming down," Lithuanian Foreign Minister Gabrielius Landsbergis told reporters as he arrived at the meeting.

With Russia having stepped up air attacks on Ukraine's energy infrastructure and cities, EU governments are under pressure to supply more protective systems to Kyiv. But countries that have U.S.-made Patriots - which Ukraine already uses and values highly for their ability to shoot down fast-moving ballistic missiles - were non-committal on Monday.

Since Kyiv began a push for more Patriots in recent weeks, Germany has been the only EU country to pledge an extra battery. Berlin is also leading a drive to get more air defence from other countries for Ukraine, through donations of equipment and financial contributions.

Other European countries including Greece, the Netherlands, Poland, Romania, Spain and Sweden also have Patriot systems.

— Reuters

Global military spending hit all-time high in 2023, report finds

Global military spending reached a record high of $2.44 trillion in 2023 after jumping 6.8% from 2022 amid a "global deterioration in peace and security," the Stockholm International Peace Research Institute (SIPRI) said in a report on Monday.

Ukraine and Russia topped the list for the countries that increased their military spending the most in 2023, by 51% and 24%, respectively. Russia's actual military expenditure remained far above that of Ukraine at an estimated $109 billion.

This figure is likely an underestimation, the report noted, as Russia's financials are highly opaque, and the budget allocated to military spending is supplemented by businesses, individuals and organizations.

Ukraine's military spending meanwhile totaled around $64.8 billion — around 59% the amount of Russia's spending, but 37% of Ukraine's GDP, the report said. The figure does not include the tens of billions of military aid that Kyiv receives, which narrow the gap between its expenses and those of Russia.

Read the full story here.

— Sophie Kiderlin

Difficult period coming for Ukraine in mid-May, intelligence chief says

Ukraine will face a difficult period on the front in the mid-May, early June period when Russia is expected to launch a new and wider offensive, the head of Ukrainian military intelligence told the BBC.

"A rather difficult situation awaits us in the near future. But it is not catastrophic, this must also be understood. Armageddon will not happen, as many are now beginning to say. But there will be problems from mid-May," Kyrylo Budanov told the BBC Ukrainian service in an interview published Monday

Ukrainian officials have already warned that they expect Russian forces to launch a new offensive in early summer.

"The Russians will use a comprehensive approach. They conduct a complex operation ... it will be a difficult period. Mid-May, early June," Budanov told the BBC in an interview conducted on April 19, a day before the U.S. House of Representatives approved a $61 billion aid package for Ukraine.

Budanov was confident Ukraine would win the war despite forthcoming challenges.

"The coming period, in our opinion, will be difficult. But difficult and catastrophic are different things. We've been through tough times several times, and we'll get through this one, believe me. Nothing extraordinary will happen. We know all their plans in advance," he said, without providing further details.

CNBC was unable to verify Budanov's claims.

Russian Foreign Minister Sergei Lavrov hinted last Friday that Russian forces would try to seize the city of Kharkiv in northeast Ukraine in a future significant Russian offensive operation. He's the first senior Kremlin official to outright identify the city as a potential Russian operational objective in a summer offensive.

Russia wants to establish a demilitarized so-called "sanitary zone" in the border areas of Ukraine to protect Russia's southwestern regions from attack.

— Holly Ellyatt

Russia claims second gain in two days in Ukraine's Donetsk region

Russia said on Monday its forces had taken control of the village of Novomykhailivka 40 km (25 miles) southwest of the Ukrainian city of Donetsk, the second advance it has announced in two days.

Reuters could not independently verify the Russian gain, reported by the defence ministry. Ukraine's General Staff said in its regular morning report that Kyiv's forces continued to hold back Russian attempts to advance near the village.

Russia's defence ministry said in a statement that its Southern group of forces had fully taken Novomykhailivka "and improved the tactical situation along the front line".

On Sunday Russia said it had taken control of the settlement of Bohdanivka, further to the north. Bohdanivka lies northeast of Chasiv Yar, a strategic town located on high ground which, if captured, could open up the way for Russia to advance on several "fortress cities" in eastern Ukraine.

The Russian gains, if confirmed, underline the urgency for Ukraine of taking delivery of more than $60 billion in new U.S. military aid that the House of Representatives approved on Saturday. It is expected to be approved this week by the Senate and signed into law by President Joe Biden.

Ukrainian President Volodymyr Zelenskyy urged Washington on Sunday to quickly turn the bill into law and proceed with the actual transfer of weapons, saying long-range arms and air defence systems were top priorities.

The Kremlin said on Monday that the new U.S. aid would not change the situation on the front lines. The influx of weapons should improve Kyiv's chances of averting a major Russian breakthrough in the east, military analysts say, but Kyiv still faces manpower shortages on the battlefield.

— Reuters

Russia warns world is on the brink of a 'direct military clash between nuclear powers'

Russian Foreign Minister Sergei Lavrov warned Monday that Russia and the West are on the brink of a potential nuclear confrontation.

"Westerners are dangerously balancing on the brink of a direct military clash between nuclear powers, which is fraught with catastrophic consequences," the minister said in a video message to the participants of the Moscow Nonproliferation Conference, news agency RIA Novosti reported.

Lavrov was reported as stating that the support of nuclear powers France, the U.S. and U.K. for Ukraine posed a serious strategic risk for Russia.

"Of particular concern is the fact that it is the 'troika' of Western nuclear states that are among the key sponsors of the criminal Kyiv regime, the main initiators of various provocative steps. We see serious strategic risks in this, leading to an increase in the level of nuclear danger," he said.

Russia repeatedly falsely describes Kyiv as a "criminal" regime in order to discredit and delegitimize the government. Ukraine's international allies say they are helping Ukraine to fend off Russia's unprovoked aggression and invasion that was launched over two years ago.

Lavrov said the world was experiencing a crisis in the system of arms control, disarmament and nuclear non-proliferation and that in order to prevent a further deterioration of a global crisis, joint efforts "were required to build an updated international security architecture based on the principles of multilateralism, equality and indivisibility," RIA Novosti noted.

"Only in this way is it possible to reduce the level of interstate conflict and ensure real progress in the field of arms control," Lavrov noted.

As relations between the West and Russia have deteriorated, the arena of arms control has become a frequent bone of contention and source of divergence, with several arms treaties between the U.S. and Russia abandoned or close to collapse.

— Holly Ellyatt

Kremlin says seizing frozen Russian assets would be illegal

The Kremlin said on Monday that any move by the United States to seize frozen Russian assets would be illegal, set a dangerous precedent and be challenged in court.

Kremlin spokesman Dmitry Peskov said such a move would constitute an encroachment on private and state property and would lead to retaliation and legal action.

Separately, Peskov said fresh U.S. aid to Ukraine will not change the situation on the frontlines, where Russia has claimed to have the upper hand.

— Reuters

Russia slams U.S. aid package, saying it will 'ruin Ukraine'

Russia has, predictably, reacted angrily to a new U.S. $61 billion aid package for Ukraine, claiming that it will only lead to more carnage in the conflict.

Kremlin spokesperson Dmitry Peskov said Saturday that the U.S. House of Representatives' approval of further aid to Ukraine "will make the United States of America richer, further ruin Ukraine and result in the deaths of even more Ukrainians, the fault of the Kyiv regime," Russian news agency Tass reported.

Russian Foreign Ministry spokesperson Maria Zakharova said the wider aid package, which also includes aid for Israel and Taiwan, will aggravate global crises.

"The military aid earmarked by the United States for Ukraine, Israel and Taiwan will exacerbate the global crises, as the military aid to the Kiev regime is direct financial support of terrorist activity, [the aid] to Taiwan is an interference in China's domestic affairs and to Israel is a direct path to the unprecedented escalation in the region," she wrote on her Telegram channel.

Two years after its invasion of Ukraine, Russia accuses Kyiv of "terrorist activity" for conducting sporadic drone and missile attacks against its territory and energy infrastructure. Ukraine rarely comments on such attacks but, like Russia, says it does not target civilian infrastructure.

— Holly Ellyatt

Kyiv breathes a sigh of relief after aid package, but says time is of the essence

Ukrainian President Volodymyr Zelenskyy thanked U.S. lawmakers in the House of Representatives for passing a vital $61 billion aid package for Ukraine last weekend, saying the aid "will keep the war from expanding, save thousands and thousands of lives, and help both of our nations to become stronger."

He asked that the bill, which will be passed to the Senate, be approved as quickly as possible.

"The time between political decisions and actual damage to the enemy on the front lines, between the package's approval and our warriors' strengthening, must be as short as possible," Zelenskyy said on social media platform X.

The aid is a lifeline for Ukraine, whose forces in the east of the country have had to ration their usage of shells amid shortages of supplies. Russian forces have been making gains in the Donbas region, with Ukraine pleading for more air defense systems, artillery and ammunition to turn the tide in the war.

Matthew Savill, the Military Sciences Director at London-based defense think tank RUSI, commented that while the package — and the boost to morale and ammunition stocks — will be welcome for the Ukrainian military, "the main point is that this funding can probably only help stabilise the Ukrainian position for this year and begin preparations for operations in 2025," he said in emailed comments.

"Predictability of funding through 2024 and into 2025 will help the Ukrainians plan the defence this year, especially if European supplies of ammunition also come through, but further planning and funds will be required for 2025, and we have a U.S. election between now and then," he added.

— Holly Ellyatt

U.S. House passes $95 billion Ukraine, Israel aid package, sends to Senate

The U.S. House of Representatives on Saturday with broad bipartisan support passed a $95 billion legislative package providing security assistance to Ukraine, Israel and Taiwan, over bitter objections from Republican hardliners.

The legislation now proceeds to the Democratic-majority Senate, which passed a similar measure more than two months ago. U.S. leaders from Democratic President Joe Biden to top Senate Republican Mitch McConnell had been urging embattled Republican House Speaker Mike Johnson to bring it up for a vote.

The Senate is set to begin considering the House-passed bill on Tuesday, with some preliminary votes that afternoon. Final passage was expected sometime next week, which would clear the way for Biden to sign it into law.

The bills provide $60.84 billion to address the conflict in Ukraine, including $23 billion to replenish U.S. weapons, stocks and facilities; $26 billion for Israel, including $9.1 billion for humanitarian needs, and $8.12 billion for the Indo-Pacific, including Taiwan.

Ukrainian President Volodymyr Zelenskiy expressed his thanks, saying U.S. lawmakers moved to keep "history on the right track."

"The vital U.S. aid bill passed today by the House will keep the war from expanding, save thousands and thousands of lives, and help both of our nations to become stronger," Zelenskiy said on X.

The Biden administration is already finalizing its next assistance package for Ukraine so it can announce the new tranche of aid soon after the bill becomes law in order to meet Ukraine’s urgent battlefield needs, a White House official said.

— Reuters