Credit: Mark Lennihan/AP Photo

T-Mobile is finally promising LTE service in the United States, but customers won't get the faster data speeds until next year.

The company has announced its plans to roll out the high-speed broadband network in 2013.

While specific details on the timing aren't being revealed, T-Mobile's chief technology officer, Neville Ray, told reporters that the goal is to cover the top 50 markets in the U.S. with the high speed connectivity by the end of 2013.

T-Mobile will be the last of the four major carriers to roll out LTE, which brings much faster data speeds to phones, tablets and laptops. (Note: you need an LTE capable phone to take advantage of the faster speeds.) Verizon was the first to deploy its network and AT&T joined late last year. Sprint plans to roll its network out later this year.

It hasn't been an easy run for T-Mobile: AT&T's effort to acquire the carrier was rejected by the government in December and it's the only carrier in the U.S. to not offer the iPhone to its customers.

Earlier today T-Mobile USA CEO Philipp Humm acknowledged that "it was a tough year for us," adding,  "The AT&T deal negatively impacted customer satisfaction, that's why we believe it is important to reinvigorate the Challenger strategy and to relaunch the brand."

While LTE won't hit until 2013 for T-Mobile customers, Humm is focused on rebuilding T-Mobile this year with strong devices, including smartphones and tablets, and improved voice and data experiences.

But that doesn't solve the problem that many have jumped to carriers like Sprint, Verizon, and AT&T to get the iPhone. Humm admitted that the company lost a net 526,000 subscribers in the fourth quarter.

The iPhone is "a good device and we have always said we'd like to have it on the right terms," Humm said.