Federal Reserve Chairman Ben Bernanke issued a double-barreled warning on the American economy, saying the housing market will continue to struggle and the Fed sees “significant risks” in the leveragedbuyout boom.

Mr. Bernanke, speaking at a conference in Chicago yesterday, said curbs on subprime lending “are expected to be a source of some restraint on home purchases and residential investment in coming quarters.” And he said the Fed is “beginning to look at” what he called “the risks that are associated with working with private-equity firms.”

The Fed chief’s comments suggest the central bank has raised its guard against a second credit bubble emerging in the form of leveraged buyouts at a time when the American economy is dealing with the mortgage bust. Lawmakers and consumer advocates have blamed the Fed and other regulators for lax enforcement while lenders wrote a record $2.8 trillion in mortgages from 2004 to 2006.

“You learn from experience,” a chief economist at Moody’s Investors Service Inc. in New York, John Lonski, said. “The theme here would be whenever you have higher-risk borrowing accelerate considerably, the risks of unexpected debt-repayment problems rise.”

The Fed chairman maintained his forecast that the slump in housing won’t have a broader impact on the economy, comments that were echoed by former Fed chief Alan Greenspan today. “We do not expect significant spillovers from the subprime market to the rest of the economy or financial system,” Mr. Bernanke said.

Fed officials this year have cited the housing recession as a main risk to economic growth, which was the weakest in four years last quarter. Mr. Bernanke’s comments today reflect the consensus of policy makers that the downturn in housing is unlikely to cause consumers to cut spending.