WASHINGTON - U.S. President George W. Bush, hosting major polluting nations last week, sought to convince skeptics that he wants to help shape the next global deal on climate change, despite his long history of shunning such efforts.

But with only 15 months left in office, his chances of becoming a major player in the debate over climate change are diminishing quickly, analysts and diplomats said.

They added that his resistance to the kind of mandatory emissions limits sought by many allies in Europe and Japan may further weaken his influence as negotiations intensify over a successor treaty to the Kyoto Protocol. That treaty, which Bush rejected, expires in 2012.

Bush told a gathering of envoys from the 17 biggest emitters of greenhouse gases that he took global warming seriously and that the United States would do its part to combat it.

His acknowledgment of a problem highlighted a shift from his previous questioning of the science linking human activity to rising temperatures.

But Bush found himself at odds with many of the invited delegates as he tried to rally support for voluntary measures and declined to embrace the binding targets many believe are essential to tackling global warming.

"I think there was a lot of hope that the United States would show some movement," said Alex Lennon, a national security analyst and climate specialist at the Center for Strategic and International Studies.

Now, Lennon said, "a lot of countries are already looking past this administration."

A European participant in the two-day climate session echoed that sentiment. "I know that with this administration we will not reach any results because the time is too short," the visiting official said, speaking on condition of anonymity.

OUTSIDER STATUS

In another indication that Bush has failed to shed his status as an outsider in climate talks, he skipped a high-profile meeting on the subject at the United Nations a few days before the Washington session. He did attend a U.N. working dinner on climate, however.

When Bush first proposed convening a series of meetings of major emitters in May, many worried it was an attempt to undermine the U.N. negotiations on climate.

The countries attending the Washington session together account for 80 percent of the global economy and 80 percent of global emissions. They include large European countries such as Britain and Germany as well as fast-growing developing countries like China, India and Brazil.

"The mere fact that this meeting took place is a sign that the administration has changed its tune," said Charles Kupchan, professor of international relations at Georgetown University.

Still, Kupchan added, "The agenda he laid out for addressing the problem falls well short of what many industrialized countries -- particularly the Europeans -- would like to see."

Bush tried to overcome some of the skepticism about the gathering by emphasizing that he hoped it would help build momentum for the U.N. talks. The next set of U.N. negotiations are to take place in December in Bali.

Just one month before that, Bush will host German Chancellor Angela Merkel at his ranch in November and is sure to find himself in the familiar role of facing pressure to support tougher climate steps.

But the message Merkel brings may be aimed as much at the American public as at Bush himself.

In the years since Bush rejected the 1997 Kyoto treaty, the debate within the United States has shifted toward growing concern about global warming.

The Democratic-led Congress is considering several bills that would set mandatory emissions limits. Prominent corporations like General Electric and DuPont are calling for strong action on global warming, as are some Republican politicians such as California Gov. Arnold Schwarzenegger.

That has led many to many to believe that the president who succeeds Bush in early 2009 is almost certain to be more sympathetic to a tougher approach on climate change.

"I don't think that anyone believes that the next president -- whether Republican or Democrat -- will follow Bush's lead on climate," said Nicholas Eisenberger of Green Order, a New York consulting firm that advises companies on climate issues.

"The question for President Bush is whether he has anything relevant left to say," Eisenberger said. "If he does not, the world will just move on without him."