Boris Johnson has conceded that it is “touch and go” whether the Cop26 climate conference will be a success.
He said it was “very far from clear” that the necessary commitments would be made at the international climate summit, which begins on Sunday in Glasgow, Scotland.
Mr Johnson told a press conference of young children that Cop26 would perhaps be the most important summit the UK has had “in our lifetimes”.
“We need as many people as possible to go to net zero so that they are not producing too much carbon dioxide by the middle of the century,” he said.
“Now, I think it can be done. It’s going to be very, very tough, this summit.
“And I’m very worried, because it might go wrong and we might not get the agreements that we need.”
Mr Johnson said “peer pressure” at the UN summit could force some nations into action.
But with some major world leaders including China’s Xi Jinping expected to stay away, the chances of that tactic being a success may be limited.
It will be the biggest climate conference since the 2015 Paris summit and is seen as crucial in setting worldwide emission targets to slow global warming, as well as firming up other key commitments.
Mr Johnson also argued that recycling “doesn’t work” because it doesn’t address the root problem.
He said: “Recycling isn’t the answer. Recycling … it doesn’t begin to address the problem.”
The only answer is “to cut down on our use of plastic”, he said.