Emmanuel Macron has announced he still hopes to convince an isolated Donald Trump to change his mind on the Paris Climate Agreement.
The US President announced his decision to withdraw from the landmark 2016 deal last month - the only world leader to do so.
The declaration was met with widespread criticism from the international community, who said it jeopardised action against global warming.
All leaders of the planet's richest 20 nations - besides Mr Trump - used the summit to declare the Paris deal "irreversible" and requiring action "swiftly".
Theresa May said she was "dismayed" by the US withdrawing from the agreement and hoped Mr Trump would change his mind.
Angela Merkel, who hosted the summit in Hamburg, said she "deplored" the decision, and thought it was unlikely the US would rejoin.
A communique, on behalf of the G20 members, singled out the US for its withdrawal, saying they "took note" of the position.
“The leaders of the other G20 members state that the Paris Agreement is irreversible," the document said.
"We reiterate the importance of fulfilling the UNFCCC [UN Framework Convention on Climate Change] commitment by developed countries in providing means of implementation including financial resources to assist developing countries with respect to both mitigation and adaptation actions in line with Paris outcomes and acknowledge the OECD’s report 'Investing in Climate, Investing in Growth'.
"We reaffirm our strong commitment to the Paris Agreement, moving swiftly towards its full implementation in accordance with the principle of common but differentiated responsibilities and respective capabilities, in the light of different national circumstances and, to this end, we agree to the G20 Hamburg Climate and Energy Action Plan for Growth as set out in the Annex.”
Ms Merkel said it was "very clear" that member states had not reached a consensus but differences were "clearly stated".
The US joined the states of Nicaragua and Syria in rejecting the Paris Climate Agreement when Mr Trump announced his decision in June.
“I am elected to represent the citizens of Pittsburgh, not Paris,” he told an audience at the White House. He said the Paris deal "hamstrung" the US and endangered jobs.
International leaders decried the action, with Mr Macron responding to the action with a call to 'Make the Planet Great Again,' mocking Mr Trump's election slogan, 'Make America Great Again'.
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