WASHINGTON — Under pressure from federal regulators, Fannie Mae’s board has agreed to sweeping action to correct what were cited as serious accounting problems.

Fannie Mae agreed to boost the mortgage giant’s capital, recalculate key transactions back to 2001, and tighten internal controls.

Experts said yesterday that the agreement could crimp profits, slow growth, or force the sale of assets at the nation’s largest financer of home mortgages.

The government-chartered mortgage financer and its regulator said yesterday they had reached an agreement late Sunday after negotiations last week and over the weekend.

A week ago, the Office of Federal Housing Enterprise Oversight told Fannie Mae its eight-month investigation had found pervasive earnings manipulation to meet Wall Street expectations as well as serious accounting misdeeds. It ordered “immediate remedial action.”

“This agreement is an important step toward resolving these concerns and helping to assure safe and sound operations,” Ofheo Director Armando Falcon said in a statement yesterday.

A Treasury official, meanwhile, renewed the Bush administration’s call for tighter government reins over Fannie Mae and Freddie Mac, the other huge government-sponsored mortgage company, which faced an accounting crisis 15 months ago.

“We think the legislation needs to be re-enacted, and the sooner the better,” the assistant Treasury secretary for financial institutions, Wayne Abernathy, told reporters. He said action by lawmakers might even be possible in the few remaining weeks before Congress adjourns.Key Republican senators and House members also have urged such a measure, which the two politically influential companies have lobbied against for years.

The housing oversight regulators last week raised the possibility of removing top management of Washington-based Fannie Mae, the second-largest American financial institution after Citigroup Inc.That’s still possible.

The revelations pushed down Fannie Mae’s stock more than 13%, to a 52-week low, in a three-day slide last week. The shares stabilized yesterday, rising 99 cents to close at $66.50 on the New York Stock Exchange.

Neither the regulators nor the company said whether Fannie Mae would have to restate its earnings. Freddie Mac wound up having to restate $4.5 billion in earnings for 2000-2002, which mostly had been understated.

Under the agreement, Fannie Mae will increase, within the next nine months, its cushion of reserve capital, needed in case future problems arise, by about $5 billion.

To raise that money, Fannie Mae has several options. It could issue new stock; sell assets from its portfolio of investments; or even scale back its purchase of home mortgages.