US President Donald Trump has cast doubt on a report by his own government warning of devastating effects from climate change.

Asked outside the White House about the findings that unchecked global warming would wreak havoc on the US economy, he said: "I don't believe it."

The report found that climate change will cost the US hundreds of billions of dollars annually and damage health.

The Trump administration has pursued a pro-fossil fuels agenda.

The world's leading scientists agree that climate change is human-induced and warn that natural fluctuations in temperature are being exacerbated by human activity.

He told reporters on Monday that he had "read some of" Friday's report, which was compiled with help from US government agencies and departments.

Mr Trump said other countries must take measures to cut their emissions.

"You're going to have to have China and Japan and all of Asia and all these other countries, you know, it [the report] addresses our country," he said.

"Right now we're at the cleanest we've ever been and that's very important to me.

"But if we're clean, but every other place on Earth is dirty, that's not so good.
"So I want clean air, I want clean water, very important."

Former Democratic presidential candidate Hillary Clinton accused the Trump administration of trying to hide the report.

The Fourth National Climate Assessment outlines the potential impacts of climate change across every sector of American society.

"With continued growth in emissions at historic rates, annual losses in some economic sectors are projected to reach hundreds of billions of dollars by the end of the century - more than the current gross domestic product (GDP) of many US states," the report says.

"Without substantial and sustained global mitigation and regional adaptation efforts, climate change is expected to cause growing losses to American infrastructure and property and impede the rate of economic growth over this century."

The report notes that the effects of climate change are already being felt in communities across the country, including more frequent and intense extreme weather and climate-related events.

But it says that projections of future catastrophe could change if society works to reduce greenhouse gas emissions and "to adapt to the changes that will occur".