PARIS (AFP) - President Donald Trump's plan for gutting domestic climate change policies is now on the table, but his administration left open on Wednesday (March 29) the question of whether it will turn its back on the landmark Paris Agreement.
The suspense could last for some time, perhaps until the G7 meeting of world leaders in late May, or even the July G20 in Germany, experts say.
In the meantime, business leaders, governments and climate activists everywhere are speculating feverishly on what it would mean for the fight against global warming if Washington were to pick up its climate marbles and go home.
Some are even wondering how much damage team Trump could do from within the fold if it opted to stay put.
"Everyone has taken on board the fact that we have entered a zone of turbulence," Laurence Tubiana, CEO of the European Climate Foundation and, as France's former climate ambassador, one of the treaty's main architects, told AFP.
One thing seems clear already: The United States under Trump - who has vowed to remove restrictions on coal-fired power plants and shelve more stringent vehicle emissions standards - will be hard put to honour its core Paris commitments.
These include cutting US greenhouse gas emissions by at least 26 per cent below 2005 levels by 2025, and giving billions of dollars in aid for poor countries trying to curb their own emissions and cope with climate impacts.
The 196-nation treaty vows to cap global warming as "well below" 2 deg Celsius compared to late 19th-century levels, a goal scientists describe as daunting.
The rapidly falling price of renewable energy, gains in efficiency, and a market-driven shift from coal to natural gas will all help to constrain future US emissions.
But Trump's actions "make it virtually impossible for the United States to fulfil its nationally determined contribution," the name given to voluntary pledges made by all countries under the treaty, said Bob Ward, policy director at the Grantham Research Institute on Climate Change and the Environment, in London.
At the same time, Trump's so-called "skinny budget", unveiled earlier this month, singled out UN climate funds for axing, a campaign promise that a Republican Congress will almost certainly help him keep.
For now, at least, there are no signs that Trump's open contempt for the Paris Agreement - which, as a candidate, he pledged to "cancel" - has caused defections from the ranks.
"I don't see any other country that looks as if it would pull out or formally disavow their commitments," said Alden Meyer, director of strategy and policy for the Union of Concerned Scientists in Washington.
Both China and the European Union sought to shore up the pact's foundation on Wednesday.
"The world can count on Europe to maintain global leadership in the fight against climate change," said Miguel Arias Canete, European Union Commissioner for Energy and Climate Action.
China's foreign ministry spokesman Lu Kang said his country "will honour its obligations 100 per cent."
Both powers, experts note, are eager to fill any void created by the United States, especially in the burgeoning market for renewables driving the transition from dirty to clean energy.
"For the moment, the international community is holding fast," said Tubiana.
But challenges on the near horizon could shake that solidarity.
"By 2020, we need to ratchet up emissions reductions to have any hope of meeting the Paris temperature goals," Meyer told AFP.
"The question is what impact this might have on the willingness of countries to put more on the table." .
Those discussions will begin in earnest next year, but this time - unlike during the runup to the December 2015 UN climate summit that gave birth to the Paris pact - there will be no China-US duo to drive the process.
"That dynamic has been broken," said David Levai, a climate policy analyst at the Institute Sustainable Development And International Relations in Paris.
Countries that dragged their feet then - Saudi Arabia, India, Japan - "might hide behind the Americans going forward," he told AFP.
If Trump did keep the United States within the UN climate fold, the US agenda would likely include boosting fossil fuels.
"It is very encouraging to hear a US President talk positively about the role of clean coal technology," said Benjamin Sporton, CEO of the World Coal Association in London.
"I think there is a huge opportunity if the US stays in the Paris Agreement to help raise the profile of low-emissions coal technologies," he told AFP.
Most scientific scenarios for capping global warming at under 2 deg C give a prominent role to such technologies, especially so-called carbon capture and storage, or CCS.
But some analysts fear that Trump could seek to derail the process from within.
"There is no signal yet that is the stance they are planning to take," said Meyer.
"But if the US goes into active resistance mode - then that would be worse than if it dropped out entirely."