The world's fossil fuels will "obviously" have to stay in the ground in order to solve global warming, Barack Obama's climate change envoy said on Monday.
In the clearest sign to date the administration sees no long-range future for fossil fuel, the state department climate change envoy, Todd Stern, said the world would have no choice but to forgo developing reserves of oil, coal and gas.
The assertion, a week ahead of United Nations climate negotiations in Lima, will be seen as a further indication of Obama's commitment to climate action, following an historic US-Chinese deal to curb emissions earlier this month.
A global deal to fight climate change would necessarily require countries to abandon known reserves of oil, coal and gas, Stern told a forum at the Center for American Progress in Washington.
"It is going to have to be a solution that leaves a lot of fossil fuel assets in the ground," he said. "We are not going to get rid of fossil fuel overnight but we are not going to solve climate change on the basis of all the fossil fuels that are in the ground are going to have to come out. That's pretty obvious."
Last week's historic climate deal between the US and China, and a successful outcome to climate negotiations in Paris next year, would make it increasingly clear to world and business leaders that there would eventually be an expiry date on oil and coal.
"Companies and investors all over are going to be starting at some point to be factoring in what the future is longer range for fossil fuel," Stern said.