Germany doesn't see any reason to scrap the nuclear deal reached between Iran and six powers in 2015 and would do everything possible to uphold it, Foreign Minister Heiko Maas said on Monday.

"We continue to believe that this agreement makes the world safer and without this agreement the world would be less safe," Maas said at a joint news conference with his visiting French counterpart.

"We fear a failure would result in an escalation," Maas said.

U.S. President Donald Trump has threatened to pull out of the Iran deal by not extending sanctions waivers when they expire on May 12, unless European signatories of the accord fix what he calls its "flaws".