NEW YORK (AFP) - Bank of America said Friday it was buying Countrywide Financial in a four-billion-dollar deal, rescuing the nation's largest mortgage lender from near-bankruptcy in a housing crisis.

The deal eased fears of collapse of the largest player in the troubled US mortgage market that could have sent shock waves through the world's biggest economy.

Bank of America offered 0.1822 of its own shares for each Countrywide share, according to a statement from the number-one US bank by stock market share value.

Analysts said that would put Countrywide's share value at 7.16 dollars, below its close Thursday at 7.75 dollars.

Countrywide's woes had reflected the troubles of the overall US housing market as the big lender had been hit by the meltdown in real estate, especially the subprime market to borrowers with weak credit histories.

Countrywide shares had rallied Thursday after a report said Bank of America was in "advanced talks" to buy the troubled mortgage lender, which in October posted its first quarterly loss in 25 years amid a mortgage credit crisis due to the collapse of a real-estate boom.

But the market was less than impressed by the news early Friday. Countrywide slid to 6.50 dollars in electronic trading ahead of the New York session's opening bell.

In August, when mortgage-related woes started to roil financial markets, Bank of America bought a stake of 16 percent in Countrywide and had first right of refusal in any sale of the beleagured mortgage lender.

Countrywide, which has been the subject of bankruptcy rumors for several months, "will benefit from the stability of being part of the largest and one of the most financially strong financial institutions in the United States," Bank of America said in a statement.

"Countrywide presents a rare opportunity for Bank of America to add what we believe is the best domestic mortgage platform at an attractive price and to affirm our position as the nation's premier lender to consumers," Bank of America chairman and chief executive Kenneth Lewis said in the statement.

Countrywide operates more than 1,000 field offices and has a sales force of nearly 15,000. The purchase includes the Calabasas, California-based company's insurance and other businesses.

Countrywide had 408 billion dollars in mortgage originations in 2007 and has a servicing portfolio of about 1.5 trillion dollars with nine million loans, Bank of America said.

Bank of America said it expects the transaction will be finalized in the third quarter and forecast the combined company would have after-tax synergy savings of 670 million dollars in the 2009-2011 period.

The Charlotte, North Carolina-based bank said the deal would have a neutral effect on its 2008 results and be a positive factor in 2009, excluding merger and restructuring costs.

Both companies' boards of directors have backed the deal, which is subject to approval by Countrywide's shareholders and regulators, it said.

Investors reacted with caution to Bank of America's modest takeover offer, apparently concerned about potential further losses in the pipeline at Countrywide. Bank of America shares were down 0.51 percent at 39.10 dollars in pre-market trading.

"The acquisition should be good news for the overall market as it reduces the potential for more bad news out of Countrywide and implies that Bank of America is in reasonably good shape in terms of credit issues if it is comfortable taking on Countrywide," said Dick Green at Briefing.com.

"The deal is being viewed with understandable skepticism, however," he added.

Analysts have been cutting estimates for Countrywide's fourth quarter. The company has projected a profit, but some began to doubt that possibility and began forecasting losses amid Countrywide's rising delinquencies.