Macron assailed the "maximum pressure" policy of US President Donald Trump, saying it had failed, AFP reported.
"We will not compromise on the activation of a mechanism that the United States is not in a position to activate on its own after leaving the agreement," Macron told the 75th Session of the UN General Assembly by video from Paris, in a reference to the Iran 2015 nuclear deal with world powers.
"This would undermine the unity of the Security Council and the integrity of its decisions, and it would run the risk of further aggravating tensions in the region," he warned.
The Trump administration says it is "snapping back" virtually all UN sanctions on Iran lifted under the nuclear accord with Tehran, negotiated under former president Barack Obama but which Trump abandoned in 2018.
Washington says it can reimpose the sanctions because it is still a "participant" in the accord, a position denounced by Europe as legally untenable.
Macron insisted that France, along with its European allies Britain and Germany, would keep up its demand for "full implementation" of the Iran nuclear deal.
Iran began gradually rolling back parts of its obligations under the deal a year after the US unilateral pullout to push the European parties to live up to their own commitments and protect Iran against sanctions.