A US envoy has signaled that President Donald Trump may be ready to soften his stance on the Paris climate pact, a European official said at a summit in Canada on Saturday.

Any shift in the US position on the historic deal could be hugely significant, after Trump announced in June that he was abandoning the 2015 agreement.

The United States "stated that they will not renegotiate the Paris Accord, but they try to review the terms on which they could be engaged under this agreement," said the European Union's top climate official Miguel Arias Canete.

He said there would be a meeting on the sidelines of next week's UN General Assembly with American representatives "to assess what is the real US position," but noted "it's a message which is quite different to the one we heard from President Trump in the past."

Environment ministers from some 30 countries gathered in Montreal on Saturday to push forward on implementing the Paris climate deal without the US.

The United States was represented only by an observer, who was not immediately available for comment.

All the ministers present and the US observer agreed that the Paris accord was irreversible, French Ecology Minister Nicolas Hulot said.

Trump, whose country is the world's second biggest producer of greenhouse gases after China, drew widespread criticism when he announced on June 1 that he would quit the climate pact.

He has said he wanted to renegotiate the massive agreement, which was originally signed by every nation except Syria and Nicaragua.

The actual withdrawal time from the pact is three years, allowing time for a US re-think.

In August, the Trump administration confirmed it was abandoning the Paris accord but the State Department then indicated Washington was still committed to reducing its greenhouse gas emissions and engaging with the international community on combating climate change.

Source: AFP