France President Emmanuel Macron is in Japan for bilateral talks ahead of the G20 summit.

France will not sign any final statement at this week's G20 summit that does not commit to ambitious climate goals, President Emmanuel Macron said Wednesday, calling climate issues a "red line".

Climate change is likely to be among many contentious issues on the table at the meeting in Japan's Osaka on June 28-29, with Washington expected to oppose strong references to the Paris climate accord, from which it plans to withdraw.

"If we do not talk about the Paris accord and if, in order to find agreement among the 20 in the room, we are not able to defend climate ambitions, it will be without France," Macron told a meeting of French citizens in Tokyo.

Nearly 200 nations have signed the Paris climate agreement, which commits signatories to efforts to cap global warming at "well below" two degrees Celsius (3.6 Fahrenheit).

But US President Donald Trump has said he will withdraw Washington from the deal, a process which will take several years.

Macron is in the Japanese capital for bilateral talks ahead of the G20 summit, which is set to be dominated by disputes over trade as well as tensions with Iran.

But the member nations are also likely to struggle for common ground on climate change, Trump's administration bucking a global consensus on the issue.

Macron referred to increasing international pressure for action on the issue, including by youth activists, and said he would not bow to pressure for a unanimous statement that omitted mention of the Paris agreement.

"If one or the other of them doesn't want to sign, they can say so, but we must not collectively lose our ambition," the French leader added.