U.S. Democratic presidential candidate Barack Obama met Sunday with T. Boone Pickens, a billionaire oilman and Republican, to discuss the future of U.S. energy policy.

Before the meeting in Reno, Nevada, Senator Obama dismissed questions about Pickens's involvement in the 2004 presidential election. Pickens contributed $3 million to a group called "Swift Boat Veterans for Truth," which sought to discredit the Vietnam war service of then-Democratic presidential nominee John Kerry.

The attacks were seen as a factor in President George Bush's 2004 victory.

Pickens has endorsed neither Obama nor Republican candidate John McCain. Pickens is promoting a national energy plan that relies on natural gas to cut U.S. dependence on foreign oil.

Pickens met last week with Senator McCain, who had no public appearances scheduled Sunday.

Some information for this report was provided by AP, Bloomberg and Reuters.