US President Donald Trump has told "confidants", including the head of the Environmental Protection Agency Scott Pruitt, that he plans to leave a landmark international agreement on climate change, the Axios news outlet reported on Saturday, citing three sources with direct knowledge.

On Saturday, Trump said in a Twitter post he would make a decision on whether to support the Paris climate deal next week.

The White House did not immediately respond to a request for comment.

A source who has been in contact with people involved in the decision told Reuters a couple of meetings were planned with chief executives of energy companies and big corporations and others about the climate agreement ahead of Mr Trump's expected announcement later in the week. It was unclear whether those meetings would still take place.

"I will make my final decision on the Paris Accord next week!" he tweeted on the final day of a Group of Seven (G7) summit in Italy at which he refused to bow to pressure from allies to back the landmark 2015 agreement.

The summit of G7 wealthy nations pitted Mr Trump against the leaders of Germany, France, Britain, Italy, Canada and Japan on several issues, with European diplomats frustrated at having to revisit questions they had hoped were long settled.

Mr Trump, who has previously called global warming a hoax, came under concerted pressure from the other leaders to honour the 2015 Paris Agreement on curbing carbon emissions.

Although he tweeted that he would make a decision next week, his apparent reluctance to embrace the first legally binding global climate deal that was signed by 195 countries clearly annoyed German Chancellor Angela Merkel.

"The entire discussion about climate was very difficult, if not to say very dissatisfying," she told reporters. "There are no indications whether the United States will stay in the Paris Agreement or not."