The fact that 2008 is a presidential election year reduces the chance that a US bill to fight global warming will become law, he said.

Bingaman, a New Mexico senator who has sponsored a measure to limit emissions of greenhouse gases that warm the planet, said Bush's stance is hurting US standing in the international community.

Calling last week's White House-sponsored meeting of the world's biggest greenhouse polluters a non-event, Bingaman said he heard complaints privately from delegates who called it a waste of time.

"For the United States to have a leadership role in this whole discussion, we're going to have to do something ourselves to demonstrate our own commitment to dealing with the problem," Bingaman said.

"Until that happens, until we can adopt a cap and trade system economy-wide or take some significant step to start controlling greenhouse gas emissions, we're not going to be deferred to in any serious way by the international community on this subject."

'IT AIN'T HAPPENING'

Frank O'Donnell of the environmental advocacy group Clean Air Watch was more blunt than Bingaman in assessing the chance of a climate change law during the Bush administration.

"I think the likelihood of real legislation being enacted in this Congress is about as likely as a complete troop withdrawal from Iraq during President Bush's term in office," O'Donnell told the summit.

"In other words, it ain't happening."

The White House supports voluntary curbs on emissions and standards set by each country, rather than a global agreement for mandatory limits, which most other countries want.

Bingaman said the notion of voluntary limits is "not a credible argument" and is similar to voluntary speed limits for drivers. "If you want something to work, you have to put in mandatory limits," he said.

The issue of global warming is growing in the US public view, he said, but has not been debated much in the early days of the presidential campaign, at least partly because most Democratic candidates agree on the topic and Republicans are largely keeping quiet about it.

"If the president were to change his position and embrace the idea of mandatory limits ... on greenhouse gases, I think you'd see several Republicans immediately follow that policy who are now holding back," Bingaman said.

As to various state measures geared to limiting global warming, he said these were helpful at this stage.