Warren Buffett (search), the billionaire investor who has publicly criticized President Bush's tax cuts as favoring the wealthy, said Sunday he has agreed to serve as an economic adviser to John Kerry (search ).

Buffett, a Democrat, said he and Kerry have spoken once — when Kerry called to ask if Buffett would be willing to serve with a group of advisers that includes Roger Altman, deputy treasury secretary under President Clinton, and former Clinton economic adviser Gene Sperling (search ).

Neither Kerry nor anyone on the Massachusetts senator's economic advisory team have asked so far Buffett's opinion on economic policy, Buffett said, adding that he expects to hear from the other advisers soon.

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"It's fairly likely that I will hear from a few people at some point," he said. "I'm available if anybody wants my opinion on anything."

Buffett, chairman of Berkshire Hathaway Inc., served on an economic advisory panel last year for then-California gubernatorial candidate Arnold Schwarzenegger (search ), a Republican, drawing criticism when he suggested that California's property taxes were too low. Schwarzenegger quickly dismissed Buffett's suggestions.

Buffett also lent political assistance in the past to former Nebraska Sen. Bob Kerrey, who ran for president in 1992 but lost the Democratic nomination to Bill Clinton.