WASHINGTON: The US economy is probably due for two strong quarters of economic growth to close out 2009, but the recovery may falter next year, former Federal Reserve Chairman Alan Greenspan said.

"I think we're OK for the next six months," Greenspan said. "We are getting a recovery in (housing) starts and motor vehicles, but the process doesn't have legs to it."

Auto sales and housing, normally the driving forces behind economic recovery, got a boost from government efforts such as the $3 billion "cash-for-clunkers" trade-in program, which encouraged consumers to buy new cars, but it may not be sustainable.