Following FCC chairman Julius Genachowski's official show of opposition to AT&T's proposed buyout of T-Mobile, AT&T said last night that it will take a $4 billion accounting charge in the fourth quarter to cover a breakup fee to T-Mobile should the deal fail to gain regulatory approval.

AT&T and T-Mobile parent Deutsche Telecom also said they've withdrawn their pending approval applications to the FCC "to facilitate the consideration of all options at the FCC and to focus [the companies'] continuing efforts on obtaining antitrust clearance for the transaction from the Department of Justice either through the litigation pending before the United States District Court...or alternate means."

In August, the Justice Department filed a lawsuit to block the buyout.

And on Wednesday, Genachowski asked the other four FCC commissioners to approve an administrative hearing on the proposed deal, during which AT&T would have to show how the merger was in the public interest.

In a briefing with reporters at the time, FCC officials said the merger would create an "unprecedented" level of concentration in the wireless market and that it was impossible to see how the deal could serve the public.

The $4 billion charge announced by AT&T includes $3 billion in cash and $1 billion worth of spectrum.

"As soon as practical, AT&T and Deutsche Telekom intend to seek the necessary FCC approval," AT&T said in its statement.