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.