California Gov. Arnold Schwarzenegger predicted Friday that an international deadlock over how to deal with global warming will end once President Bush leaves office, while a leading expert warned of dire consequences if urgent action is not taken.

Schwarzenegger spoke at a conference at Yale University in which 18 states pledged to take action on climate change. He noted a dispute over whether the U.S. should commit to reducing its greenhouse gas emissions before China and India do the same.

"But I think the deadlock is about to be broken," said Schwarzenegger, a Republican like Bush.

Schwarzenegger said all three president candidates would be great for the environment and predicted progress after one is inaugurated.

Schwarzenegger has been at odds with the Bush administration over a 2002 California law to reduce greenhouse gas emissions. The U.S. Environmental Protection Agency blocked the law from taking effect in California and 16 other states, saying global warming is not unique to the state and that emission goals should be set nationally.

Bush called for a halt Wednesday in the growth of greenhouse gases by 2025, acknowledging the need to head off serious climate change. The plan came under fire immediately from environmentalists and congressional Democrats who favor mandatory emission cuts, a position also held by all three presidential contenders.

Bush for the first time set a specific target date for U.S. climate pollution reductions and said he was ready to commit to a binding international agreement on long-term reductions as long as other countries such as China do the same.

Dr. R. K. Pachauri, chairman of the Nobel Prize-winning United Nations' Intergovernmental Panel on Climate Change, warned that without action to curb global warming agricultural yields would fall and flooding and heat waves would become more intense. Some species could become extinct, he said.

Pachauri said measures to curb warming are not expensive.

"The myth that there will be a loss of jobs and economic output needs to be exploded," Pachauri declared.

Pachauri praised the efforts of governors to deal with the issue.

"But there is a need for the country as a whole to move forward," Pachauri said.

The governors of Connecticut, California, Kansas and New Jersey were at Yale on Friday along with two Canadian premiers to review state programs and develop a strategy to combat global climate change.

"If we can move the states forward toward serious action it is a very substantial commitment and a very significant step toward the start of a thoughtful and serious response to address the problem of climate change," said Daniel Esty, director of the Yale Center for Environmental Law and Policy.

Esty said the 18 states that signed a declaration committing themselves to action together produce as much emissions as Europe's four biggest economies.

Among other things, the declaration says the states recommit themselves to the effort to stop global warming and call on congressional leaders and presidential candidates to work with them to establish a comprehensive national climate policy.

"Rewarding and encouraging meaningful and mandatory federal and state climate action is the key to success," the declaration states.

It also pledges to reach out to the presidential candidates to shape the first 100 days of the next administration.

The states signing the declaration are: Arizona, California, Colorado, Connecticut, Delaware, Florida, Illinois, Kansas, Maine, Maryland, Massachusetts, Michigan, New Jersey, New Mexico, New York, Oregon, Virginia and Washington.