NEW YORK — T-Mobile and MetroPCS have agreed to combine their struggling cell phone businesses in a deal aimed at letting them compete better with their three larger rivals.

The combined company will use the T-Mobile brand and have about 42.5 million subscribers. Although T-Mobile will stay No. 4 among U.S. wireless companies, it will get access to more space on the airwaves, a critical factor as cell phone carriers try to expand their capacity for wireless broadband.

That could ultimately mean more choices and better services for customers, though Forrester Research analyst Charles Golvin doesn’t believe the deal will make a “revolutionary difference” for U.S. cell phone customers. That said, MetroPCS customers will probably have to buy new phones at some point over the next three years as they are moved over to T-Mobile’s network.

Both companies have faltered in the highly competitive U.S. cell phone market led by Verizon Wireless and AT&T Inc. T-Mobile has 33.2 million subscribers, well behind No. 3 Sprint Nextel Corp’s 56 million. MetroPCS is even further back, ranking fifth with 9.3 million.

Last year, T-Mobile USA’s German parent, Deutsche Telekom AG, tried to sell the U.S. cell phone business to AT&T for $39 billion. Getting more access to airwaves was the main reason AT&T wanted T-Mobile.

But regulators rejected that proposed purchase, worried that competition would suffer if the second-largest cell phone company were to gobble up the fourth.

Under the new deal, Deutsche Telekom will hold a 74 percent stake in the combined company, while MetroPCS Communications Inc. shareholders will own the remainder. MetroPCS shareholders will also receive a payment of about $1.5 billion.

The deal still has to be approved by shareholders of both companies and will require government approval. But the regulatory concerns this time appear to be much milder than they had been with AT&T. T-Mobile and MetroPCS are both relatively small, and T-Mobile has been losing subscribers for the past two years.