AT&T Inc has asked a U.S. court to dismiss cases brought by rivals Sprint Nextel Corp and Cellular South against AT&T's proposed $39 billion purchase of T-Mobile USA.

The U.S. Department of Justice has also sued to block the deal, which would vault AT&T into a leading position in the U.S. wireless market through the purchase of No. 4 operator T-Mobile USA, a unit of Deutsche Telekom AG.

AT&T, the No. 2 U.S. mobile service, argued in a document filed on Friday at the U.S. District Court for the District of Columbia that the court should dismiss the case due to Sprint's lack of standing in its argument that the deal would hurt competition in the U.S. wireless market.

Sprint cannot wrap itself in the cloak of wireless service consumers' interest because Sprint is not a consumer but instead a competitor in the sale of wireless services, the filing said.

Sprint said it was not surprised by the filing, which it said was without merit. It said it would respond next Friday.

AT&T also argued that Cellular South did not have a case and used a business proposal from Cellular South to argue against the smaller company's case.

AT&T included in its filing a copy of an email from Cellular South's Chief Executive Hu Meena asking AT&T to alleviate its concerns about the merger by entering a type of network sharing agreement with Cellular South in the state of Mississippi and another other states.

This inappropriate proposal confirms that what Cellular South fears is competition, not lack of competition, AT&T said in its filing. It also included another email from Meena disputing AT&T's interpretation of the first email.

(Reporting by Sinead Carew, editing by Gerald E. McCormick)