US President Donald Trump on Thursday described the air in India and China as "filthy" as he denounced Democratic rival Joe Biden's plans to tackle climate change.
At their second and final presidential debate, Trump renewed his criticism that action on climate change was unfair to the United States.
"Look at China, how filthy it is. Look at Russia, look at India -- it's filthy. The air is filthy," Trump said at the debate in Nashville.
Trump charged that Biden's climate plan was an "economic disaster" for oil states such as Texas and Oklahoma.
Biden said that climate change is "an existential threat to humanity. We have a moral obligation to deal with it."
"We're going to pass the point of no return within the next eight to 10 years," he said.
The planet has already warmed by around one degree Celsius (34 degrees Fahrenheit) from pre-industrial levels, enough to boost the intensity of deadly heat waves, droughts and tropical storms.
Trump has pulled the United States out of the Paris climate accord, which aims to cap global warming "well below" two degrees Celsius.
Trump's remarks come days before Secretary of State Mike Pompeo and Defense Secretary Mark Esper visit New Delhi for talks on building the growing US-India partnership.
At the first presidential debate, Trump also spoke critically of India, questioning its coronavirus data amid criticism of his handling of the pandemic.
China's foreign ministry on Friday said Beijing hoped the US would "stop dragging China into its election campaigns."
Defending the capital's air quality, foreign ministry spokesman Zhao Lijian told reporters "the sky outside is azure today."
China's average urban concentration of PM2.5 air pollutants -- particles small enough to enter the bloodstream -- has dropped in recent years.
But last year it still accounted for 48 of the world's 100 most polluted cities, according to a Greenpeace and IQAir Group report.