The sour US economy is unlikely to rebound before 2009, billionaire investor Warren Buffett said Friday.

He said the credit crunch will continue to worsen, and noted that Federal Reserve Chairman Ben Bernake doesn’t have a “magic wand” to strengthen the economy and tame inflation.

“You always find out who’s been swimming naked when the tide goes out,” Buffett told CNBC. “We found out that Wall Street has been kind of a nudist beach.”

Buffett appeared on CNBC as part of the promotion of a documentary called I.O.U.S.A. The documentary argues the nation could face economic disaster if it doesn’t get a handle on its growing debt.

Buffett said U.S. stocks are now “more attractive” than they were a year ago. He said that his company, Berkshire Hathaway (BRK-A), bought stock valued at $3.98 billion in the second quarter and has no bets against the dollar.

Berkshire Hathaway likes blue chip companies such as American Express (AXP) and Wells Fargo (WFC). Buffett said he bought more stock in one of these companies, but declined to say which one.

Buffett said he goofed by selling 61% of Berkshire Hathaway’s stake in Anheuser-Busch (BUD) for $61 to $62 a share. In July, the brewer agreed to be taken over by Belgium’s InBev for $70 a share.

Buffett said there was a “reasonable chance” that Fannie Mae (FNM) and Freddie Mac (FRE) shareholders will be wiped out in any reorganization, but the companies are too big to fail.