Iran has agreed to release French researcher Roland Marchal, held since June 2019, in a prisoner swap for an Iranian engineer wanted by the US over sanctions charges. Marchal's colleague, French-Iranian Fariba Adelkhah, remains in prison in Tehran.
Marchal is due to arrive in France around midday on Saturday, a French presidency official said.
French President Emmanuel Macron urged Iran to also release French citizen Fariba Adelkhah, who is still imprisoned, the official added. Adelkhah also holds an Iranian passport.
Iran and France have agreed to swap Marchal, held on security charges, and an Iranian detained by Paris over alleged violations of U.S. sanctions against Tehran, Iranian state media reported on Friday.
France has released Jalal Ruhollahnejad, an Iranian engineer wanted by U.S. authorities over sanctions charges, state broadcaster IRIB has reported.
France had demanded that Iran release Marchal, a senior researcher at Sciences Po university whose arrest was reported by Paris in mid-October.
In May, a French court approved the extradition of Rouhollahnejad to the United States to face charges of attempting to illegally import U.S. technology for military purposes on behalf of an Iranian company which U.S. officials said was linked to the elite Revolutionary Guards.
The detentions have complicated ties between the two countries during a period when Macron was seeking to defuse tensions between Washington and Tehran.
Iran Revolutionary Guards have arrested dozens of dual nationals in recent years, mostly on espionage charges.
The detentions have coincided with a protracted standoff with Western powers prompted by a U.S. decision to withdraw from an international agreement to curb Iranian nuclear activities.