American Home Mortgage Investment Corp. shares plunged 90 percent after the lender said it doesn’t have cash to fund new loans, stranding thousands of home buyers and putting the company on the brink of failure.

Investment banks cut off credit lines, leaving American Home without money yesterday for $300 million of mortgages it had already promised, the Melville, New York-based company said in a statement today. It anticipates that $450 million to $500 million of loans probably won’t get funded today, and the lender may have to sell off its assets.

“They can’t function without access to capital,” said Bose George, an analyst with KBW Inc. in New York. “The company either has to file for bankruptcy or go through some type of rescue or restructuring, and either way will leave almost nothing for the common shareholders.”

American Home caters to borrowers whose credit scores fall just short of standards for top-rated mortgages. The announcement provides fresh evidence that defaults may be spreading from subprime borrowers with the worst credit scores to homeowners with more reliable payment records. The biggest U.S. mortgage lender, Countrywide Financial Corp., said last week late payments rose among some of its most creditworthy clients.

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