The former action star used the UN World Environment Day conference, attended by mayors from the world's most populous cities, to announce the plan that comes despite Washington's refusal to ratify the Kyoto Protocol on the environment.

He formally launched the gathering with a signing of an executive order mandating that greenhouse gas emissions in California be cut to year 2000 levels in the next five years, and that they be 80 percent below 1990 levels by 2050.

"California will continue to be a leader in the fight against global warming and protecting our environment," the movie tough guy told the conference where he stole the show and received a standing ovation.

"Today I am establishing clear and ambitious targets to reduce greenhouse gas emissions in our state to protect our many natural resources, public health, agriculture and diverse landscape.

"By working together we can meet the needs of both our economy and environment," added the Republican politician who came to power after a special election in October 2003.

The move to slash greenhouse gas emissions in environmentally-conscious California comes after his fellow Republican, President George W. Bush, refused to put the Kyoto Protocol to Congress for ratification.

The global environmental pact aimed at reducing greehouse gases was signed by US former vice president Al Gore in 1998 and came into force in February.

It imposes reductions of emission of six gases: including carbon dioxide and methane, but the emissions targets vary for each industrialised nation that signed the accord.

"If we don't start right now, it will be too late," Schwarzenegger said of his intent to save clean air, crystal waters and magnificent mountains like those he knew growing up in his native Austria.

"The march of progress does come with consequences," he said. "Here is one area where we must turn back the clock: the environment."

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