President Donald Trump made a brief unscheduled appearance on Monday at the UN climate summit, which he had been expected to skip entirely.
The US president, who has repeatedly expressed doubt about the overwhelming scientific consensus on manmade causes of global warming, was due to attend a separate conference on religious freedom.
However, he first dropped in on the climate summit, where he spent just a few minutes.
Dozens of world leaders were discussing measures to try and slow down ever-more dangerous trends in climate change.
Trump, who withdrew the United States from a major international pact on reducing greenhouse gas outputs, did not speak.