A US Navy veteran is returning home after being freed from detention in Iran.
Michael White was sentenced to prison last year on unspecified charges, but was released temporarily on medical grounds to the Swiss embassy in March.
He was arrested in 2018 after travelling to meet his girlfriend in the Iranian city of Mashhad.
His release came on the day that Iran's foreign minister announced the return from the US of an Iranian doctor.
US officials have yet to confirm the release of Majid Taheri, but a third man - an Iranian scientist detained in the US - was deported to Iran earlier this week.
Sirous Asgari, a materials science professor from Tehran, had been charged in 2016 with trying to trade secret research from an American university, but was acquitted in November.
The releases appear to be a rare example of co-operation between Iran and the US - although Washington has denied so far that it was a straight prisoner swap.
US President Donald Trump confirmed on Thursday that Mr White had been freed and the Swiss plane he was travelling on had left Iranian airspace.
"I will never stop working to secure the release of all Americans held hostage overseas," he said.
I just got off the phone with former American hostage Michael White, who is now in Zurich after being released from Iran. He will be on a U.S. plane shortly, and is COMING HOME...— Donald J. Trump (@realDonaldTrump) June 4, 2020
"For the past 683 days my son, Michael, has been held hostage in Iran by the IRGC [Islamic Revolutionary Guards Corps] and I have been living a nightmare," Mr White's mother said in a statement. "I am blessed to announce that the nightmare is over, and my son is safely on his way home."
Both Mr White's family and President Trump thanked Switzerland for its help.
The 48-year-old was one of at least six US citizens either imprisoned in Iran or out on bail.
He was granted medical furlough to the Swiss embassy in March amid the release of large numbers of prisoners due to the spread of coronavirus in Iran.
His family said he had visited the country a number of times before he was detained.
"We look forward to reuniting him with his family," US Secretary of State Mike Pompeo said on Thursday.
"[We] will not rest until we bring every American detained in Iran and around the world back home to their loved ones," he added.
In December, the US and Iran conducted a prisoner swap in a rare sign of co-operation. Chinese-American researcher Xiyue Wang and Iranian scientist Massoud Soleimani were freed.
Relations between the two countries have been increasingly hostile since the US abandoned the Iran nuclear deal in 2018.
But tensions escalated further this year when the US assassinated top Iranian commander Gen Qasem Soleimani in a drone strike in Iraq in January. Iran retaliated by launching ballistic missiles at Iraqi military bases hosting US forces.