Iran freed four Americans including a Washington Post reporter on Saturday in a prisoner swap, as diplomats gathered to announce the lifting of international sanctions and bring the country of 80 million people back to the global economic stage.
"Implementation day" of the nuclear deal marks the biggest re-entry of a former pariah state into world commerce since the end of the Cold War.
The four held in Iran include Washington Post bureau chief Jason Rezaian, held since 2014 and convicted in Iran of espionage.
His case in particular has been a notable obstacle to a thaw in Iranian-US relations.