President Donald Trump said that the US could "go back" into the Paris climate deal on Wednesday - having withdrawn America from the global accord last year.
"We could conceivably go back in ... I feel very strongly about the environment," said the President during a joint news conference with Norway's Prime Minister Erna Solberg.
The agreement was signed under former President Barack Obama's administration in December 2015 by nearly 200 countries to curb global carbon emissions and contain global warming to 2℃.
Mr Trump began the withdrawal process in June last year but it will not officially conclude per the terms of United Nations-brokered agreement until just before the 2020 US election.
Neil Bhatiya, a researcher at the DC-based think tank Center for a New American Security, said, the administration has not been able to articulate a criticism of the Paris agreement that reflects what the agreement actually says. He explained that the US "has a lot of flexibility" in determining exactly how to reduce emissions to meet the agreed-upon targets in the Paris accord.
Also, ahead of the signing the Obama administration's team had been insistent on language which would make the agreement entirely voluntary and not make the Paris Agreement a treaty - which would have required Congressional approval and been legally binding. In other words, the accord is entirely voluntary.
The leaders of France, Germany and Italy issued a joint statement voicing “regret” about Trump’s move, promising to redouble their efforts to implement the Paris agreement and asserting that it cannot be renegotiated.
“We deem the momentum generated in Paris in December 2015 irreversible and we firmly believe that the Paris Agreement cannot be renegotiated, since it is a vital instrument for our planet, societies and economies,” read the statement from French President Emmanuel Macron, German Chancellor Angela Merkel and Italian Prime Minister Paolo Gentiloni.
It was not clear from his comments on Wednesday whether he has embarked on any attempt to renegotiate America's terms.
French President Emmanuel Macron in December said he would not agree to a renegotiation but was hopeful the US would return to the accord.
Last September, the US was present as an observer when environment ministers from about 30 countries discussed key issues relating to the Paris agreement in Montreal, Canada.
Analysts have said the US withdrawal from the Paris agreement makes it more difficult for the world to reach the goals that it set for itself in the Paris agreement.
The deal unites all the world's nations in a single agreement on tackling climate change for the first time in history.
Coming to a consensus among nearly 200 countries on the need to cut greenhouse gas emissions is regarded by many observers as an achievement in itself and has been hailed as "historic".
Pledges thus far could see global temperatures rise by as much as 2.7℃, but the agreement lays out a roadmap for speeding up progress.
● To keep global temperatures "well below" 2.0℃ (3.6℉) above pre-industrial times and "endeavour to limit" them even more, to 1.5℃
● To limit the amount of greenhouse gases emitted by human activity to the same levels that trees, soil and oceans can absorb naturally, beginning at some point between 2050 and 2100
● To review each country's contribution to cutting emissions every five years so they scale up to the challenge
● For rich countries to help poorer nations by providing "climate finance" to adapt to climate change and switch to renewable energy.
The Kyoto Protocol of 1997 set emission cutting targets for a handful of developed countries, but the US pulled out and others failed to comply.
However, scientists point out that the Paris accord must be stepped up if it is to have any chance of curbing dangerous climate change.
The national pledges by countries to cut emissions are voluntary, and arguments over when to revisit the pledges - with the aim of taking tougher action - have been a stumbling block in the talks.
The pact promises to make an assessment of progress in 2018, with further reviews every five years.
As analysts point out, Paris is only the beginning of a shift towards a low-carbon world, and there is much more to do.
"Paris is just the starting gun for the race towards a low-carbon future," says WWF-UK Chief Executive David Nussbaum.
Prof John Shepherd of the National Oceanography Centre, University of Southampton, says the agreement includes some welcome aspirations but few people realise how difficult it will be to achieve the goals.
“With unremitting efforts of all parties, we adopted here an equitable and reasonable, comprehensive and balanced, ambitious, durable and effective, and legally binding Paris Agreement,” said Xie.
“The Paris Agreement is a hard-won result which represents the broadest consensus of the international community and should be cherished and upheld by all parties. ”