By John Whitesides, Political Correspondent

WASHINGTON (Reuters) - Presidential rivals Barack Obama and John McCain shifted the campaign focus back to the faltering U.S. economy on Monday, with Obama convening an all-star panel of advisers to help him hatch new approaches to a deepening problem.

Obama met in Washington with a group that included billionaire investor Warren Buffett, who participated by telephone, former Federal Reserve Chairman Paul Volcker and Google Chairman Eric Schmidt.

The meeting came as the Bush administration projected the U.S. budget deficit would rise to a new record of $482 billion (241.8 billion pounds) in fiscal 2009, which starts October 1, 2008, as a continued economic slowdown cuts into government revenues.

The rising deficit is certain to complicate matters for the winner of November's presidential election, with either Obama or McCain dealing with the fallout of a collapsing housing market, soaring gas and food prices and deeper job uncertainty.

"The challenges we're facing could not be more critical," Obama, a Democratic senator from Illinois, said as the meeting opened.

"The economic emergency is growing more severe, jobs are down, wages are falling, the financial markets threaten to be engaged in a protracted credit crunch with long-lasting ramifications," he said.

McCain's campaign countered with a conference call in which top economic adviser Carly Fiorina told reporters the Republican has been "quietly talking" with economists and policymakers, including Federal Reserve Chairman Ben Bernanke and Treasury Secretary Henry Paulson, over the past year.

"I think the American people are getting treated to yet another photo op by Barack Obama, but meanwhile John McCain has been out talking about the economy, understanding the economy, taking advice on the economy for many, many months," Fiorina said.