Hours after receiving another government lifeline, Bank of America posted a fourth-quarter loss of $1.79 billion on Friday, down from net income of $268 million a year earlier, in a reversal caused largely by growing consumer loan losses.

And bigger troubles came from Merrill Lynch, which Bank of America hastily snapped up in September for $50 billion. A fresh round of write-downs at Merrill pushed that firm into a $15.3 billion loss for the fourth quarter. That was the firm’s sixth troubled quarter since the credit crisis began. Merrill was among the most aggressive — and most harmed — by mortgage investments.

Merrill’s results for the fourth quarter are not a part of Bank of America’s. The merger of the two banks closed on Jan. 1.

In a conference call Friday morning, analysts asked Kenneth D. Lewis, the bank’s chairman, whether he had regrets that he had agreed to purchase Merrill.

Mr. Lewis said that as Merrill’s fourth-quarter losses mounted, he did re-evaluate whether he should close the deal and whether he could renegotiate the price for Merrill. But, he said, regulators implored him to complete the transaction and said they would provide support.

“The government was firmly of the view that terminating or delaying the closing of the transaction could lead to significant concerns and could result in significant systemic concerns,” Mr. Lewis said. “We did think we were doing the right thing for the country.”

Still Mr. Lewis expressed optimism about the conglomerate he has built, once the economy recovers.

“This company will generate huge amounts of profit when we get a normal economic environment, not even a great one but a normal one, and so it’s almost directly related to how fast you think the economy will come back,” he said.

Bank of America’s shares, which have fallen sharply over the last week, were down sharply again on Friday, shedding $1.15, or 14 percent, to close at $7.17.

In the conference call, Bank of America executives also discussed the government assistance that was announced overnight to help them complete the merger with Merrill.

Two weeks after closing its purchase of Merrill Lynch at the urging of federal regulators, the government cemented a deal at midnight Thursday to supply Bank of America with a fresh $20 billion capital injection and absorb as much as $98.2 billion in losses on toxic assets, according to people involved in the transaction.

The bank had been pressing the government for help after it was surprised to learn that Merrill would be taking a fourth-quarter write-down of $15 billion to $20 billion, according to two people who have been briefed on the situation, in addition to Bank of America’s rising consumer loan losses.

The second lifeline brings the government’s total stake in Bank of America to $45 billion and makes it the bank’s largest shareholder, with a stake of about 6 percent.

The program is modeled after a larger one engineered to stabilize Citigroup as its stock price plummeted in late November, but it appears to have had limited success. Under the terms, Bank of America will be responsible for the first $10 billion in losses on a pool of $118 billion in illiquid assets, including residential and commercial real estate and corporate loans, and that will remain on its balance sheet.

The Treasury Department and the Federal Deposit Insurance Corporation will take on the next $10 billion in losses. The Fed will absorb 90 percent of any additional losses, with Bank of America responsible for the rest.

In exchange for the new support, Bank of America will give the government an additional $4 billion stake in preferred stock. It has also agreed to cut its quarterly dividend to a penny, from 32 cents, and accept more stringent restrictions on executive pay.

The F.D.I.C. announced separately that it would soon propose to extend its guarantee on supporting new consumer lending to 10 years, from 3 years.

“The U.S. government will continue to use all of our resources to preserve the strength of our banking institutions and promote the process of repair and recovery and to manage risks,” regulators said.

With losses mounting in the financial industry, other banks may eventually feel compelled to turn to the government for assistance, and the program could to used for other big banks. Taxpayers could end up guaranteeing hundreds of billions of dollars of banks’ toxic assets.

“The financial services sector still needs more equity,” said Frederick Cannon, the managing director at Keefe, Bruyette & Woods. “TARP was announced in mid-September and most of the initial decisions were based on the state of the economy then. The economy has gotten a heck of a lot worse.”