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 the incoming French President Emmanuel Macron, the Chinese foreign ministry said in a statement.
US President Donald Trump is still deciding whether to withdraw from it as he promised during his campaign.
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.
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.
The 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.