Aug. 21 (Bloomberg) -- The U.S. economy is at risk of dipping again after the government’s stimulus package runs out next year, Harvard University economist Martin Feldstein said.

“The economy is still weak and it’s not at all clear that the upturn that we’ve seen recently is the beginning of a sustainable rise,” Feldstein said today in an interview on Bloomberg Television in Jackson Hole, Wyoming. “There’s a serious danger that come the end of this year and the beginning of next year we will see it slipping back down again.”

Feldstein endorsed Federal Reserve Chairman Ben S. Bernanke for a second term at the U.S. central bank after his current term ends in January.

“He certainly deserves it. He has done a remarkably creative job of dealing with these problems,” Feldstein said. “They have kept credit going” and “the Fed has stepped in where the private markets have been absent.”

To contact the reporter on this story: Brendan Murray in Washington at brmurray@bloomberg.net

Last Updated: August 21, 2009 09:31 EDT