T-Mobile and Sprint are in active talks about a merger, though negotiators are still weeks away from finalizing a deal to unite the nation's No. 3 and No. 4 wireless carriers, people close to the situation told CNBC.

T-Mobile parent Deutsche Telekom would emerge as the majority owner in the stock-for-stock merger. Sprint's parent company is Softbank.

The companies declined to comment on the report.

A big factor looming over a possible deal is the risk of rejection by antitrust regulators.