French President Emmanuel Macron has said he believes President Donald Trump will bring the US back into the Paris deal on combating climate change.
But Mr Macron says he will not agree to the president's demand that America's terms should be negotiated.
He made his comments in a CBS interview on the eve of a summit on climate he has arranged on Tuesday in Paris.
Mr Macron condemned the manner in which the US had signed an international deal, then withdrawn from it.
"The US did sign the Paris Agreement. It's extremely aggressive to decide on its own just to leave, and no way to push the others to renegotiate because one decided to leave the floor. I'm sorry to say that. It doesn't fly."
President Macron aspires to lead the world in fulfilling the ambition of the Paris climate accord to hold global temperature rise to well under 2C .
He told CBS he was not willing to be accused by future generations of understanding the extent of the climate problem but doing too little to solve it.
Scientists are waiting now to see whether Tuesday's summit of 50 senior ministers and prime ministers in Paris will achieve its aim of giving a boost to the current sluggish progress on cutting emissions.
There are potentially important announcements to be made on key financial issues:
- Raising cash to give poor countries clean energy
- Stopping development banks lending for new coal plants
- Insisting that firms disclose any fossil fuel assets that might be devalued if governments clamp down on emissions.
There is also a potentially important announcement that could bind the shipping industry into climate targets - so far shipping has mostly evaded new rules on emissions because of the multinational nature of the industry.
In a significant move overnight, the oil giant Exxon announced it would assess the impact of climate change on its business.
Investors controlling about 62% of shares backed a proposal led by the New York state employees' retirement fund calling for an annual assessment of the impact of technological change and climate policy on the company's operations.
We won't know until later whether the Paris meeting has really made progress with other new initiatives.
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