Chinese President Xi Jinping has vowed to protect the landmark Paris agreement, which aims to curb climate change and fossil fuel emissions.
He made the promise in a phone call with incoming French President Emmanuel Macron, the Chinese foreign ministry said in a statement.
US President Donald Trump is still deciding whether to withdraw from the accord - an election campaign promise.
Climate experts worry such a move would throw the agreement into chaos.
A White House meeting to discuss the topic on Tuesday has been postponed, amid reports of divisions among senior Trump advisers.
It is the second time the meeting has been cancelled. No new date has been given.
Team Trump divided: Analysis by Anthony Zurcher, BBC News, Washington
The current disagreement within the White House over whether the US should withdraw from the Paris climate agreement is a prime example of the much-reported palace intrigue within the Trump administration spilling out into a policy debate.
In one corner you have senior officials like strategist Steve Bannon and Environmental Protection Agency head Scott Pruitt, who are on record calling for an exit from the accord. Others, like Energy Secretary Rick Perry, have been noncommittal. Meanwhile, Secretary of State Rex Tillerson has said the US should keep a "seat at the table" and presidential adviser/daughter Ivanka Trump and son-in-law Jared Kushner are pro-Paris.
Donald Trump, while he did once tweet that global warming was a Chinese conspiracy, has largely avoided extended discussions on the subject. While his administration is steadily driving to roll back many Obama-era regulations, environmental issues as a whole seem of little interest to him.
Any White House meeting to hash out a coherent policy on the Paris agreement is destined to be contentious and with a decidedly uncertain resolution. A battle no-one is convinced they will win is one that is ripe for delay - again.
Mr Xi told Mr Macron China and France "should protect the achievements of global governance, including the Paris agreement", according to the Chinese foreign ministry.
Under former President Barack Obama, the US and China issued several joint statements on climate change, even announcing together they would sign the Paris agreement. The two countries are the world's biggest polluters.
For his part, when Mr Macron received his congratulatory phone call from the US president he told him he would also seek to defend the climate deal.
Speaking on Tuesday at a conference in Milan, Italy, Mr Obama said the US and China had to "lead the way" in the fight against climate change.
"The good news is the private sector has already made a determination that the future is clean energy," he said.
"Those things are locked in now, into the energy sector. Because of the debates taking place in the current administration the steps may be taken more slowly than they would have been done, but I'm confident," he added.
The latest comments come as climate negotiators meet in the German city of Bonn to discuss how to put the Paris agreement into practice.
Almost 200 countries have backed the agreement, which aims to keep global temperature increases "well below" 2C.
It also seeks to shift the world economy away from fossil fuels in an effort to limit floods, droughts and rising sea levels.
President Trump has previously said he believes there is no evidence that humans are responsible for climate change.
He has called for more drilling, fewer regulations and the approval of the Keystone XL oil pipeline from Canada.