French President Emmanuel Macron, who is seeking to defuse the standoff over the Iranian nuclear programme, won an assurance from Trump at last month's G7 summit in Biarritz that he was ready to meet Rouhani.

But with both Rouhani and Trump set to attend the UN General Assembly in New York next week, attacks on Saudi oil facilities that Washington blamed on Iran have caused tensions to spiral again.

"There are still lots of things to sort out before we can see how to create the conditions for the United States and Iran to enter into a negotiation," said a French presidential official who asked not to be named.

"The attack (on Saudi oil facilities) creates a new context," said the official.

Macron will meet Trump in New York and may also meet Rouhani, so long as the Iranian president's visa issues are ironed out, said the official.

Tehran-backed Huthi rebels in Saudi Arabia's southern neighbour Yemen have claimed responsibility for the attacks but French Foreign Minister Jean-Yves Le Drian said Thursday this "lacks credibility".

US Secretary of State Mike Pompeo on Wednesday denounced the strikes as an "act of war", comments seen as raising the risk of a wider conflict in the Gulf region.