MetroPCS said the talks might not result in a deal. The negotiations had been widely reported, following reports over the past two weeks that T-Mobile might tie up with MetroPCS, Sprint Nextel or satellite TV operator Dish Network. Deutsche Telekom, based in Germany, is the parent company of T-Mobile USA.

T-Mobile, the fourth-largest U.S. mobile operator, continues to lag behind its larger rivals in both subscriber numbers and deployment of a fast, next-generation LTE network. A deal to merge T-Mobile with AT&T last year was canceled after the regulators rejected the plan as anti-competitive. A breakup deal gave T-Mobile US$3 billion cash and spectrum licenses in 128 markets, but the carrier is still in catch-up mode. It plans to light up its first LTE markets next year. In the quarter ended June 30, T-Mobile reported a decline of 205,000 subscribers to 33.1 million.

MetroPCS sells flat-rate monthly plans and has 9.3 million subscribers, including about 700,000 customers on its LTE network. MetroPCS' 3G network uses CDMA, a different technology from T-Mobile's GSM-based system.

Unlike the AT&T proposal, a merger with MetroPCS would strengthen two players that have both struggled against the dominant carriers, analysts said.

"If anything, it's improving the competitive landscape," said Phil Marshall of Tolaga Research.