US President Donald Trump and and challenger Joe Biden have clashed over the country's response to climate change in their final presidential debate.
The candidates were asked at their match-up in Nashville, Tennessee, what they would do to combat climate change.
It was the first time in a presidential debate the candidates were not questioned on whether they believed in it or not.
"I do love the environment," Trump said, citing a federal program to plant trees, and a drop in carbon emissions.
But he said he was not willing to harm businesses in order to help the environment.
Meanwhile Biden said his plan to transition to a more climate-friendly economy would create high-paying jobs and boost US businesses.
"Global warming is an existential threat to humanity," Biden said on Thursday.
"We have a moral obligation to deal with it and we're told by all the leading scientists in the world we don't have much time."
Trump, who trails Biden in national opinion polls ahead of the November 3 election, accused his rival of planning to destroy the oil industry.
Biden responded by saying he did believe the country should eventually replace oil with solar, wind and other forms of non-polluting power.
"I would transition from the oil industry, yes," Biden said, prompting Trump to call for voters in states where oil is an important industry to note the former vice president's stance.
"He is going to destroy the oil industry," Trump said. "Will you remember that Texas? Will you remember that Pennsylvania, Oklahoma, Ohio?"
Republicans immediately pounced, saying Biden would kill millions of jobs.
After the debate, Biden told reporters he was referring to a plan to stop subsidising fossil fuels.
"We're not getting rid of fossil fuels," Biden said.
"We're getting of the subsidies for fossil fuels. But we're not getting rid of fossil fuels for a long time ... they're not going to lose their jobs. Besides, a lot more jobs are going to be created in other alternatives."
Trump also accused Biden of planning to ban hydraulic fracturing, a process of extracting natural gas from shale that is opposed by many environmentalists.
Biden said he would ban fracking on federal land only. Fracking is an issue in western Pennsylvania, a crucial battleground state in the election.
The president mocked a part of Biden's climate plan that called for more efficient buildings, saying Biden would "knock down buildings and build new buildings with little tiny small windows".
Environmentalists have complained for years that the candidates' views on climate change have not been emphasised in presidential debates.
But heat waves and wildfires in the western US and uncommonly powerful storms battering other parts of the country have put climate issues in the spotlight.
Australian Associated Press