Reports in the US suggest Mr Trump will withdraw the US from the deal.

UN Secretary General Antonio Guterres said that as the world's largest economy, US support was crucial.

Meanwhile, Chinese and EU leaders are set to agree a joint statement backing the Paris agreement, saying it is "an imperative more important than ever".

The statement - a draft of which has been seen by the BBC - says rising temperatures affect national security and increase "social and political fragility", while the transition to clean energy creates jobs and economic growth.

Mr Guterres told the BBC: "It is obviously a very important decision as the United States is the biggest economy in the world.

"But independently of the decision of the American government, it's important that all other governments stay the course.

"The Paris agreement is essential for our collective future and it's also important that American society - like all other societies, the business community - mobilise themselves in order to preserve the Paris agreement as a central piece to guarantee the future of our children and grandchildren."