Fifteen Democratic lawmakers asked the Obama administration on Thursday to approve AT&T Inc's proposed purchase of T-Mobile USA.

Representative Heath Shuler and 14 other Democrats sent a letter to President Barack Obama arguing that the deal, which would merge two of the four large national cellphone carriers, would reduce joblessness and encourage investment.

We urge the administration to resolve expeditiously your concerns and approve the proposed merger between AT&T and T-Mobile USA, they said in the letter dated Thursday.

The Justice Department has filed a lawsuit aimed at stopping the deal, saying the acquisition of T-Mobile USA by AT&T would lead to higher wireless prices.

The proposed deal would vault AT&T over Verizon Wireless, a venture of Verizon Communications and Vodafone Group Plc, into the No. 1 spot. T-Mobile USA is now owned by Deutsche Telekom AG.

Sprint is the third largest carrier.

The letter said the proposed deal should be approved since AT&T has pledged to bring back 5,000 jobs that it had moved overseas. The letter also pointed to a study showing that the deal could create 55,000 to 96,000 jobs during the process of integrating the two companies and doing needed upgrades.

The letter also noted AT&T's pledge to extend high-speed Internet wireless coverage to 97 percent of all Americans.

The letter was signed by 15 Democrats: Representatives Heath Shuler, John Barrow, Mike Ross, Dan Boren, Dennis Cardoza, Joe Baca, Leonard Boswell, Ben Chandler. Jim Costa, Henry Cuellar, Mike McIntyre, Mike Michaud, Collin Peterson, Loretta Sanchez and David Scott.

(Reporting by Diane Bartz in Washington; Editing by Phil Berlowitz)