REUTERS) -- AT&T is considering whether or not it will try to revise its planned purchase of T-Mobile USA, the company's first signal that it may have to give up on the proposed $39 billion merger.

Until now both AT&T and T-Mobile USA's parent Deutsche Telekom had spoken only of their efforts to fight for regulatory approval for their deal, which the U.S. Justice Department sued to block in August on antitrust grounds.

The Judge overseeing the antitrust case on Monday granted a request by both AT&T and the government for a postponement of the proceeding until January 18 while AT&T evaluates all its options.

We are actively considering whether and how to revise our current transaction to achieve the necessary regulatory approvals, AT&T said in a statement.

At a hearing last week, U.S. District Judge Ellen Huvelle questioned AT&T's desire for a speedy trial given its decision to withdraw its application for approval of the deal with the U.S. telecommunications regulator, the Federal Communications Commission.

Both the Justice Department and the FCC have said they are concerned about how the deal would impact competition in the U.S. wireless market. An AT&T purchase of No. 4 U.S. operator T-Mobile USA would vault No. 2-ranked AT&T into first place in the U.S. market.

AT&T had announced the plan to buy the smaller company in late March.

(Reporting by Diane Bartz, Sinead Carew and Nicola Leske; Editing by Richard Chang and Tim Dobbyn)