Sen. Angus King had a heated exchange with intelligence officials at the end of Wednesday's public testimony before the Senate Intelligence Committee.
King pressed acting FBI Director Andrew McCabe, National Security Agency Director Admiral Michael Rogers, and Director of National Intelligence Dan Coats on their refusal to discuss conversations with ousted FBI Director James Comey and President Donald Trump, demanding to know the legal basis of their refusal.
Rogers said he felt it was "inappropriate" to answer questions.
"What you feel isn't relevant, admiral," King fired back. "Why aren't you answering the questions? I do mean it in a contentious way."
Earlier in Wednesday's testimony, Coats said he has never felt pressure to "intervene, interfere in any way for shaping intelligence in any way."
However, when asked if he was prepared to say he had never been asked to influence an ongoing investigation, Coats said, "What I'm not willing to do is share confidential information that I think ought to be protected in an open hearing."
With their testimony coming a day before a highly anticipated hearing with Comey regarding the events that led to his firing in May, intelligence chiefs refused to answer questions regarding Trump and the ongoing Russia investigation.
The Washington Post reported Tuesday that Coats told associates Trump asked him to intervene with Comey in March.
Trump has insisted the ongoing federal investigation into possible collusion between his campaign team and the Kremlin is a "witch hunt."