The European Union and China will throw their full weight behind the Paris climate accord at a summit on Friday, EU officials said, in a bid to fill the void if the US quits the pact.
The summit in Brussels could mark a dramatic shift in global politics, with the EU taking over from the United States in working with China to fight climate change.
Signalling a new level of cooperation, the two sides will stress the "highest political commitment" to implement all aspects of the historic 2015 agreement, according to a copy of a draft joint statement seen by AFP on Wednesday.
The EU-China summit follows a tense international tour by US President Donald Trump in which he spurned pleas by his European counterparts to adhere to the deal.
US media reported Wednesday that Trump had decided to pull his country out of the accord but the unpredictable US tycoon indicated he would keep the world guessing for another few days.
"We will issue a joint statement on climate change that will stress that China and the EU... will implement the agreement," a senior EU official told reporters on Wednesday, on condition of anonymity.
"The Paris Agreement will continue with full force of implementation even if the US pulls out," he added.
Chinese Premier Li Keqiang will arrive in Brussels late Thursday for talks with EU president Donald Tusk and European Commission head Jean-Claude Juncker, with climate change at the top of the agenda.
"The EU and China consider the Paris Agreement as an historic achievement further accelerating the irreversible global low greenhouse gas emission and climate resilient development," the draft joint statement said.
"The EU and China underline their highest political commitment to the effective implementation of the Paris Agreement in all its aspects," according to the nine-page draft.
They will "significantly intensify" their political, technical, economic and scientific cooperation on climate change and clean energy to help the world shift to an economy based on low greenhouse gas emissions.
Hoping to make the climate fight a "main pillar" of their bilateral partnership, including economic relations, the two underlined that their cooperation will fuel job creation, investments and economic growth, the statement said.
Europe and China will also expand their cooperation on developing carbon markets, so-called emissions trading systems.
"If US-China climate cooperation gave birth to the Paris Agreement, now it is up to EU and China to defend and enhance it," said Li Shuo, climate policy advisor of Greenpeace East Asia.
"The pair has the potential to become the new driver for international climate diplomacy," Li said in a statement.
Former US president Barack Obama and the Chinese leadership were instrumental in building momentum toward the climate deal.
It was signed by 196 countries that set themselves goals to minimize carbon emissions and mitigate the effects of climate change.
If the United States, by most measures the world's second-biggest polluter after China, were to pull out or reduce its goals, efforts to reduce the global temperature increase might fail.
But European officials insisted that the deal would remain on track.
"I understand that if they decide to pull out it will be disappointing but I really don't think this will change the course of mankind," European Commission vice president for energy, Maros Sefcovic, said at a briefing.
"Despite this possible rollback of the US administration, Europe is ready for the leadership (on climate change) and we will definitely provide it," he added.
EU Commissioner for Energy and Climate Action Miguel Arias Canete said the world could count on European climate leadership.
"No one should be left behind, but the EU and China have decided to move forward. More on Friday," Canete tweeted.