France's Le Drian said Iran was honoring its commitments under the accord.
"The region deserves better than further destabilization provoked by American withdrawal. So we want to adhere to it and see to it that Iran does too, that Iran behaves with restraint," he told French radio station RTL.
The European Union said it would remain committed to the deal and would ensure sanctions on Iran remain lifted, as long as Tehran meets its commitments. German Foreign Minister Heiko Maas said it was "totally unclear what the U.S. envisages as an alternative to the deal."
France and others were well aware that there were concerns about issues other than nuclear capability, but they could be addressed without ditching the nuclear deal, Le Drian said.
Macron's contact with Rouhani will be followed by meetings next week, probably on Monday, involving the Iranians and European counterparts from France, Britain, and Germany.
Russia has also said it remains committed to the deal; the Russian and German foreign ministers were also due to meet in Moscow, Russian Deputy Foreign Minister Alexander Grushko said.
The prospects of saving the deal depend in large measure on whether international companies are willing and able still to do business with Iran despite the U.S. sanctions.
Le Drian said meetings would also be held with firms including oil giant Total and others with major business and economic stakes in the region.
In a harbinger of what could be in store, Trump's new ambassador to Germany said German businesses should halt their activities in Iran immediately.
French Finance Minister Bruno Le Maire said the United States should not consider itself the world's "economic policeman"
European companies including carmaker PSA, plane manufacturer Airbus, and engineering group Siemens said they were keeping a close eye on the situation.
On his official website, Khamenei said Trump's announcement of his decision had been "silly and superficial," adding: "He had maybe more than 10 lies in his comments."