AT&T, its bid to buy rival T-Mobile in trouble, is ready to make even bigger concessions to appease regulators and close the deal.

The $39 billion acquisition of T-Mobile would make AT&T the largest wireless carrier in the US.

The tie-up is being threatened by scrutiny from the Department of Justice and the Federal Communications Commission, both of which are wary of allowing one of the nation’s top telecom giants to swallow a competitor in an already small field of players.

Yesterday, it was reported that AT&T was considering selling off up to 40 percent of T-Mobile to lower the monopolistic concerns raised, especially in regions where AT&T and T-Mobile are the dominant wireless carriers.

The new aggressive sell-off plan, reported by Bloomberg, followed another tactical change from AT&T earlier this week.

The company moved to withdraw its application with the FCC, which had threatened to send the proposed merger to the courts for review.

Rather than face the judicial review and the potential disclosure of private details about the mega-merger, AT&T wanted to withdraw its FCC application and take its chances with the Justice Dept.

AT&T, in a blog post yesterday, defended that decision and fended off criticism that once filed, the papers could not be withdrawn.

“We have every right to withdraw our merger from the FCC, and the FCC has no right to stop us,” said Wayne Watts, general counsel for AT&T.

AT&T said it will sue the FCC if the commission doesn’t allow it to withdraw its application.

The merger is already under an antitrust review by the Justice Dept. The FCC imbroglio this week has caused a number of observers to declare the merger dead in the water.

The deal had been announced in March after T-Mobile’s parent company, Deutsche Telekom, agreed to terms with AT&T.

Part of those terms guarantee Deutsche Telekom up to $6 billion if the deal collapses under regulatory disapproval.