WASHINGTON —  Al Gore, the Democrats' nominee for the White House in 2000, says he has all but ruled out running for president in 2008, saying the best use of his time is to educate people about global warming.

"I haven't made a Sherman statement, but that's not an effort to hold the door open. It's more the internal shifting of gears," said Gore, referring to Civil War-era general William Tecumseh Sherman. "I can't imagine any circumstances in which I would become a candidate again. I've found other ways to serve. I'm enjoying them."

Gore referred to Sherman's famous words upon retiring from the Army in 1884, which put to rest talk of a presidential run: "If nominated I will not run; if elected I will not serve."

Gore, in an interview broadcast Sunday on ABC's "This Week," stopped short of issuing such an equivocal statement. But he said his time is best spent educating people on heat-trapping gases raising the Earth's surface temperature. He's promoting "An Inconvenient Truth," a film that chronicles his intricate slide shows on global warming.

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Vice president from 1993 to 2001, Gore ran unsuccessfully for the Democratic nomination in 1988 and narrowly lost the 2000 presidential campaign to George W. Bush, despite collecting more popular votes than the Texas Republican.

"I honestly believe that the highest and best use of my skills and experience is to try to change the minds of people in the U.S. and elsewhere in the world about this planetary emergency that we simply have to confront," Gore said.

"I have no plans to be a candidate for president again," he said. "I don't expect to ever be a candidate for president again. I haven't made a so-called Sherman statement, because it just seems unnecessary, kind of odd to do that."