FRANKFURT - Deutsche Telekom's U.S. wireless unit, T-Mobile USA, is looking at possible joint ventures with cable companies and network providers to boost its spectrum capacity.

We continue to look at JV opportunities for additional spectrum... there are a number of different options we look at, (we) have been talking with cable companies, with Clearwire, Robert Dotson, chief executive of T-Mobile USA, told analysts at an investor presentation on Thursday.

He said the company did not expect to rely on a national broadband plan the federal government is currently working on. The plan aims to expand access, increase Internet speeds and shift airwaves to mobile services.

T-Mobile USA is a distant fourth in the U.S. mobile market, behind Verizon Wireless, AT&T Inc. and Sprint Nextel Corp.

Because T-Mobile USA has been losing customers, to larger as well as smaller rivals, there was a rash of speculation last year about its future, with possibilities ranging from a merger with Sprint, Leap Wireless International Inc or MetroPCS Communications Inc, to a network partnership with Clearwire Corp.

Asked whether T-Mobile USA would consider teaming up with U.S. competitor Sprint Nextel, Dotson said: What you never want to do is take one company that is going through challenges and take another company going through challenges.

He said T-Mobile USA was not looking at how you change the configuration of the U.S. market.

Sprint is also battling subscriber losses amid tough price competition but hopes to see revenue declines slowing this year. (Reporting by Nicola Leske; editing by Simon Jessop)