The occasion was an annual tradition, the presidential photo opportunity with Nobel Prize winners. But Gore, who shared the Nobel Peace Prize for his work on the environment, was given special treatment: a private tête-à-tête with Bush, which lasted more than 30 minutes, provoking intense speculation about just what the two men talked about.

"Of course, we talked about global warming - the whole time," Gore, the former vice president, said as he and his wife, Tipper, emerged onto Pennsylvania Avenue, where they were mobbed by reporters and photographers.

No surprise there. Gore, whose documentary, "An Inconvenient Truth," won an Academy Award, is a staunch critic of the Bush administration's environmental policy. "He's constantly looking for opportunities to make an impact on this issue," said Michael Feldman, an adviser, "so being invited to the political center of the universe is a great thing for him."

"It was a private meeting," he said, "and I'm not going to say anything about it other than that it was very nice, very cordial. He was very gracious in setting up the meeting, and it was a very good and very substantive conversation. That's all."