Wall Street surged higher today after billionaire investor Warren Buffett offered to help out troubled bond insurers, easing some of the market’s concerns about further deterioration in the credit markets. The Dow Jones industrials rose about 190 points.

In an interview on CNBC, Mr. Buffett said his Berkshire Hathaway Inc. holding company has offered a second level of insurance on up to $800 billion in municipal bonds. The reinsurance offer is for bond insurers Ambac Financial Group Inc., MBIA Inc., and Financial Guaranty Insurance Co., known as FGIC.

Word of the offer gave some investors relief although Mr. Buffett says a deal would only back municipal bonds, and not the risky and complicated financial instruments that many see as more likely to have problems. Still, further assurances on the soundness of municipal bonds could help shore up Wall Street’s confidence and reinforce the differences in quality among various levels of debt.

General Motors Corp. appeared to please investors with a fresh round of buyouts to all 74,000 of its American hourly workers represented by the United Auto Workers. The company also reported losses of $38.7 billion in 2007, the largest annual loss for an automotive company.

A portfolio manager at Croft Leominster Investment Management in Baltimore, Russell Croft, said Mr. Buffett’s move gives the market a bit of needed confidence.

“It’s a good thing to see,” he said. He also agreed with Mr. Buffett’s assessment that stocks are mostly fairly valued. “We could definitely test some more lows going forward but there was a pretty good drop-off there again and I think people are trying to take advantage of it to get some quality stocks at cheaper prices.”

But some analysts were cautious.

Investors should be careful not to read too much into the market’s advance, a managing director of Westwood Capital, Len Blum, said. He noted that recent readings on American retail spending show that Americans are hurting financially.

“Stock markets will have good days in bear markets,” he said, adding that he believes more problems will be uncovered in the financial sector. “We haven’t seen all the losses. Even if you have some investors willing to bottom fish, or very sophisticated investors like Warren Buffet willing to invest at this point, the financial sector is still really sick.”

In midday trading, the Dow rose 189.08, or 1.54%, to 12,429.09.

Broader stock indicators also moved higher. The Standard & Poor’s 500 index advanced 17.30, or 1.29%, to 1,356.43, and the Nasdaq composite index rose 21.19, or 0.91%, to 2,341.25.