"The US president is not closing the door on negotiations," Putin said at the Saint Petersburg Economic Forum. "I think that all is not yet lost," he added.

Earlier this month Trump controversially pulled the United States out of the landmark 2015 pact with Iran that placed limits on its nuclear programme in return for easing economic sanctions.

Saving the deal provides a rare point of agreement between Moscow and European countries, which have seen relations tank in recent years over crises in Ukraine and Syria, as well as accusations of meddling in foreign elections and the poisoning of an ex-Russian spy in Britain.

Putin and French President Emmanuel Macron launched a joint defence of the Iranian nuclear deal on Monday but expressed differences on how to move forward as Trump weighs up whether to scrap it.

The Kremlin said Putin and Macron were both calling for "strict observance" of the hard-fought 2015 agreement after a phone call between the two leaders.

Macron's office however said that while the pair agreed on the need to "preserve the gains from the agreement", the French leader was also pushing for international talks on a potential wider deal.

Trump has derided the Iran deal as "insane" partly because its restrictions on Iran's nuclear activities begin expiring in 2025.