Actor Arnold Schwarzenegger delivers a speech during the opening of COP24 UN Climate Change Conference 2018 in Katowice, Poland. Picture: Czarek Sokolowski/AP

Katowice - Arnold Schwarzenegger says he wishes he could travel back in time like the cyborg he played in "The Terminator" so he could stop fossil fuels from being used.

"If we would've never started in that direction and used other technology, we'd be much better off," the actor and former California governor said Monday at the start of a UN climate conference in Poland.

"The biggest evil is fossil fuels: it's coal, it's gasoline, it's the natural gas," he told conference delegates.

Schwarzenegger also insisted that the United States was "still in" an international accord to curb global warming despite U.S. President Donald Trump's decision to walk away from the agreement.

Calling Trump "meshugge" - Yiddish for "crazy" - for abandoning the accord, Schwarzenegger said the 2015 agreement has widespread support at the local and state levels even if the federal government isn't on board.

"Just because Donald Trump dropped out of the Paris agreement it doesn't mean that America dropped out," he said.

"All of our states that were always environmentally friendly are still going in the same direction. All of our cities in America are going in the same direction, they are still in the Paris agreement. 

"People are investing in green technology. It's a booming industry and people should understand that we all have to work together. America is in and our crazy leader is not, so be it."

American states, cities, businesses and citizens can do a lot to curb global warming, and representatives from those arenas should be invited to next year's climate conference, he told the audience in Poland.

"And if you do that, I promise you: I'll be back," he said in another reference to "The Terminator."

In his two terms as California governor between 2003-2011, Schwarzenegger helped shape America's richest state into a green powerhouse. 

He signed legislation giving local and state officials the tools to bring down greenhouse gas emissions by reducing urban sprawl and promoting renewable energy and green technology. 

Schwarzenegger later told The Associated Press he has converted his signature Humvee trucks to run on hydrogen, electricity and biofuel and only allows himself to eat meat three days a week.

"I mean, maybe it tastes delicious, but I think we should think then and there before we eat about the world and about the pollution," he said. "So I discontinued eating meat four days a week. And eventually, maybe we'll go to seven days."

In an interview with AFP, he said he was on an "environmental crusade" and urged everyone to join in the climate fight. 

"I think governments' responsibility is to protect people. That's why we have armies to avoid an attack. Well here is the biggest attack," he told AFP. 

"Seven million people die every year because of (air) pollution, 25,000 of them die alone in America. If we don't want to fight that then there is something wrong with us."