T-Mobile said it is acquiring SunCom Wireless Holdings for $2.4 billion in a deal that will increase its market share in the southeastern United States and the Caribbean.

Announced Monday by T-Mobile's Deutsche Telekom AG parent, the acquisition will increase the population of potential customers in T-Mobile's service area from 244 million to 259 million. T-Mobile is the fourth largest U.S. wireless service provider in subscriber numbers behind AT&T, Verizon Wireless, and Sprint Nextel. T-Mobile has about 27 million subscribers and SunCom has about 1.1 subscribers.

The SunCom markets to be added include customers in North Carolina, South Carolina, Tennessee, Georgia, Puerto Rico, and the U.S. Virgin Islands. The transaction is for $1.6 billion in cash and $800 million for the assumption of SunCom debt.

Both firms use GSM/GPRS/EDGE networks and T-Mobile, noting that it had been paying SunCom roaming fees, said the acquisition is expected "to realize synergies with a net present value of approximately $1 billion through reduced roaming and operating expenses."

The acquisition is in keeping with Deutsche Telekom's strategy of adding subscribers in markets where it already has a presence. "It will round out our domestic footprint, allowing us to service 98 of the top 100 markets and will significantly benefit our financial position by reducing roaming expenses," said Robert Dotson, T-Mobile USA's president and chief executive officer, in a statement.

The acquisition has already been approved by investment funds Highland Capital Management and Pardus Capital Management, which combined own more than 50 % of SunCom's issued common stock.

SunCom's sales in the first half were $242.5 million, compared to $206.7 million in the year earlier period.