By Deborah Zabarenko, Environment Correspondent

UNITED NATIONS (Reuters) - California Gov. Arnold Schwarzenegger and former Vice President Al Gore are set to join world leaders for a U.N. meeting on Monday aimed at spurring global negotiations on how to cool a warming planet.

Schwarzenegger, a former bodybuilder and movie star who has pushed for environmental reforms in California, acknowledged that rich and poor countries have differing responsibilities when it comes to global warming, but said it is time to stop the blame game.

"The time has come to stop looking back at the Kyoto Protocol," Schwarzenegger said in remarks prepared for delivery. "The consequences of global climate change are so pressing it doesn't matter who was responsible for the past.

"What matters is who is answerable for the future. And that means all of us."

The one-day gathering is meant to send a "strong political message" about the urgency of the problem of curbing the greenhouse gas emissions that contribute to climate change, according to Secretary-General Ban Ki-moon.

It is the first of three U.S. events on climate change this week that are likely to focus attention on whether Washington can make good on its pledge to take a leading role in curbing the emissions that cause global warming.

But it is not a negotiating session. That will come in December in Bali, Indonesia, where climate experts will try to craft a successor to the emissions-limiting Kyoto Protocol, which expires in 2012.

Gore, the former presidential candidate and creator of the global warming documentary, "An Inconvenient Truth," is also to address the U.N. meeting.

U.S. President George W. Bush will not speak at this gathering, but he will dine with Ban after it ends.

Bush has rejected the Kyoto Protocol, an international agreement that requires 36 industrial nations to cut greenhouse emissions by at least 5 percent from 1990 levels by 2012.

He contends the accord unfairly burdens rich countries while exempting developing countries like China and India and that it will cost U.S. jobs.

Developing countries have said it is unfair to ask them to curb their emissions as their economies grow while industrialized nations have been polluting for decades.

Bush does plan to speak at a two-day Washington meeting at the State Department on Thursday and Friday, a gathering of "major economies" -- the world's biggest global warming contributors -- on energy security and climate change.

A third conference, the nongovernmental Clinton Global Initiative, will convene in New York from Wednesday through Friday to discuss climate change with participants from business, academia, entertainment and environmental organizations.

(Additional reporting by Jeff Mason)