The United Nations said Saturday that an Iranian-American blocked from leaving Iran can now depart and that his son was released from detention.
The United States has been pressing for the release of these two men and two other Americans amid efforts to revive the 2015 nuclear deal between Iran and major western powers.
After an appeal from UN Secretary-General Antonio Guterres, Baquer Namazi, 85, "has been permitted to leave Iran for medical treatment abroad," and his son Siamak Namazi, 50, has been released from detention, AFP quoted UN spokesman Stephan Dujarric as saying.
Baquer Namazi is a former UNICEF official who was detained in February 2016 when he went to Iran to press for the release of his son Siamak, who had been arrested in October of the previous year.
Both were convicted of espionage in October 2016 and sentenced to ten years in prison.
The father was released on medical leave in 2018 and had been serving his sentence under house arrest.
The Namazis' lawyer Jared Genser confirmed the news of the release and said the younger Namazi is now at home with his parents in Tehran for the first time in seven years.
"While these are critical first steps, we will not rest until the Namazis can all return to the United States and their long nightmare has finally come to an end," Genser said in a statement.
In June of this year the younger Namazi published a column in The New York Times in which he called on President Joe Biden to strike a prisoner swap deal with Iran, even though talks on reviving the nuclear deal were at an impasse.
The other two Americans held in Iran that Washington wants released are environmentalist Morad Tahbaz, 66, and businessman Emad Sharqi, 57.
The drive to salvage the 2015 nuclear deal resumed in late November of last year, after talks were suspended in June as Iran elected ultraconservative President Ebrahim Raisi.
The 2015 deal -- agreed by Iran, the United States, China, Russia, Britain, France and Germany -- offered Tehran sanctions relief in exchange for curbs on its nuclear program.
But the United States unilaterally withdrew in 2018 under then-president Donald Trump and reimposed biting economic sanctions, prompting Tehran to begin rolling back on its commitments.