US President Donald Trump arrived in California on Monday for briefings on the devastating wildfires scorching the Western US, after criticism from his Democrat rivals on his alleged muted response to the disaster.

Democratic presidential candidate Joe Biden, in a speech that day, branded Trump a "climate arsonist "for failing to acknowledge the role of global warming in the disaster.

Wildfires across Oregon, California and Washington have destroyed thousands of homes and a half dozen small towns since August, scorching more than 1.6 million hectares and killing at least 35 people. Fifty are reported missing in Oregon alone.

Nearly 90 wildfires are raging across the Western US, including three of the largest wildfires in California's history.

In recent comments, Trump has said poor "forest management" was primarily to blame for the uncontrolled blazes.

Upon his arrival in Sacramento to meet California Governor Gavin Newsom amid the smell of smoke in the air, Trump, in brushing off a reporter who asked if climate change was a factor in the fires, said: "I think this is more of a management situation."

Citing the experiences of other countries, he said: "They have very explosive trees, but they don't have problems like this."

Biden, criticized by Republicans for not visiting disaster areas, spoke from Delaware on the threat of extreme weather that climate scientists have said is supercharging fires.

"If we have four more years of Trump's climate denial, how many suburbs will be burned in wildfires?" Biden asked. "How many suburban neighborhoods will have been flooded out? How many suburbs will have been blown away in superstorms?"

Increasing frequency

While in California, the president maintained his long-standing position that global warming is a hoax that has little to with the increased frequency and severity of wildfires in recent years.

"It'll start getting cooler. You just watch," Trump on Monday told Wade Crowfoot, a top California state environmental official.

"I wish science agreed with you," Crowfoot responded.

"I don't think science knows, actually," the president said.

Campaigning in Nevada over the weekend, Trump blamed forest management for the current crisis. Last month he threatened to withhold federal aid from California for not implementing his ideas on forest management.

Newsom acknowledged that his state had not done enough to manage forests and that more than 100 years of fire suppression had allowed fuel to build up.

But he said global warming was driving fires and told Trump that 57 percent of forests in the state were under federal management and that only 3 percent of land in California was under state control.

"We've known each other too long, and as you suggest, (we have a) working relationship I value," Newsom told Trump. "We obviously feel very strongly that the hots are getting hotter. The dries are getting drier."

Newsom continued: "And so I think there's an area of at least commonality on vegetation, forest management. But please respect－and I know you do－the difference of opinion out here as it relates to this fundamental issue on the issue of climate change."

Trump, who has authorized federal disaster aid for California and Oregon, questioned that science.

Trump announced in 2017 that he would begin to pull the US out of the Paris Agreement on combating global warming. Biden says climate change is on his list of major crises facing the US.

"Talk to a firefighter if you think that climate change isn't real," said Democratic Los Angeles Mayor Eric Garcetti on CNN's State of the Union on Sunday. "It seems like this administration are the last vestiges of the Flat Earth Society of this generation."

In 2018, a major scientific report issued by 13 federal agencies concluded that greenhouse gas emissions from burning fossil fuels could triple the frequency of severe fires across the US West and could reduce the national economy by as much as 10 percent by the end of the century.

Agencies contributed to this story.