Pushing to fast-track its takeover of wounded home-loan giant Countrywide Financial Corp., Bank of America Corp. will promise today to help 265,000 troubled borrowers keep their homes over the next two years by refinancing or modifying at least $40 billion in mortgages.

Bank of America also plans to double its community development lending, which focuses on affordable housing, small businesses, and people in low-income and minority neighborhoods, to $1.5 trillion over 10 years, the bank’s top consumer and small-business executive, Liam McGee, said. In addition, the Charlotte, N.C.-based bank will donate $2 billion to charity over the coming decade, up 33% from its current level.

Mr. McGee is to unveil the commitments Monday while testifying at a Federal Reserve hearing into the bank’s plan to buy Countrywide, the nation’s largest mortgage lender, for $4 billion in stock. The combination would give Bank of America 25% of the American mortgage market. Regulatory approval of the deal is expected, and the bank hopes to win speedy approval and complete the acquisition in July.

Providing a preview of his testimony in an interview, Mr. McGee said he was optimistic that the company’s “responsible and principled approach” would avoid both the pitfalls of old-line banking — doing business only in supposedly safer, affluent areas — and the aggressive lending that toppled Countrywide and hundreds of lesser mortgage firms, producing a monumental wave of foreclosures.

“It’s very much our intent to make mortgages available to the underserved,” Mr. McGee said. “But we’re going to make sure that people who get loans from us can repay them and stay in their homes.”

Doing more to help mortgage holders will be the top demand of consumer and advocacy groups that are expected to crowd the two-day hearing at the Federal Reserve building in downtown Los Angeles. The Fed’s tentative witness list contained 130 names.

Prominent California advocacy groups such as the Berkeley-based Greenlining Institute said they would support speedy approval of the deal if the bank demonstrated it would lend more responsibly and do a better job of working with troubled borrowers than Countrywide.

“BofA could totally dominate the home origination market if this acquisition is approved,” president of the Greater Phoenix Urban League, George Dean, said in a statement released by Greenlining. “It therefore has a very special obligation.”

Witnesses sponsored by the San Francisco-based California Reinvestment Coalition include four borrowers complaining of frustrating delays and broken promises made by Countrywide’s bureaucracy as they struggled to make payments or fell into foreclosure proceedings. One cancer victim was promised a loan modification, then foreclosed on anyway, a spokeswoman for the coalition, Victoria Leon Guerrero, said.

“When Bank of America takes over, it will be an even bigger operation,” she said. “We want assurances they will do a better job” of handling troubled loans.

Mr. McGee said he had heard about the complaints and pledged that Bank of America would improve the level of customer service so that neither the “reality or the perception” of such difficulties would continue. He said the two companies had doubled their staffs dealing with troubled borrowers to 3,900 employees over the past year, a level he said would be maintained for at least another year.

He also noted that Countrywide, unlike many lenders, already was going beyond merely sending letters and making phone calls when borrowers run into trouble. After three missed payments on a subprime loan, Countrywide sends an employee to knock on the door of the borrower’s home to try to talk over possible solutions, Mr. McGee said.