President Donald Trump on Monday suggested global warming will reverse itself and dismissed climate change as a cause of ferocious fires engulfing swaths of the US West during a briefing with local officials in California.

Trump, who flew into Sacramento in central California on the third day of a reelection campaign swing, pushed back against state leaders who said that climate change underlies the ever-stronger blazes.

"It will start getting cooler. You just watch," he insisted to Wade Crowfoot, the head of the California Natural Resources Agency.

The official responded: "I wish science agreed with you."

This was Trump's first visit to California since the devastating blazes began there and in Washington and Oregon.

Minutes earlier, Democratic challenger Joe Biden branded Trump a "climate arsonist" whose policies are contributing to natural disasters.

On arrival in McClellan Park, near Sacramento, Trump repeated his argument that the wildfires are due instead to insufficient maintenance of forest areas to make them less combustible.

"There has to be strong forest management," the Republican said.

"With regard to the forests, when trees fall down after a short period of time, about 18 months, they become very dry. They become really like a match stick," he said. "They just explode."

But at the briefing, California Governor Gavin Newsom, a Democrat, countered that the fires are driven mostly by global warming.

Newsom acknowledged that "we have not done justice on our forest management," though he pointed out that more than half of the land in California is under federal, not state control.

But he said the overwhelming cause of the problem is far bigger.

"The hots are getting hotter, the dries are getting drier," he said. "We submit the science is in and observed evidence is self-evident: that climate change is real and that is exacerbating this."

After the briefing was over, Crowfoot sought to get the last word, tweeting: "It actually won't get cooler, Mr. President" over a graph showing relentlessly rising temperatures in California since the 1980s.