An 85-year-old Iranian-American held by Iran over internationally criticized spying charges left the country Wednesday for Oman, officials said, after increasing pressure to free him amid his struggles with poor health. His 50-year-old son, however, remains in Iran.

The release of Baquer Namazi marks the first American to be freed by Iran since President Joe Biden took office, even as talks over Tehran’s tattered nuclear deal with world powers have stalled. Iran long has used detained Westerners or those with ties abroad as bargaining chips in negotiations.

The state-run IRNA news agency published video of Namazi boarding a Royal Oman air force jet, apparently in Tehran. It said Namazi left the country Wednesday.

Flight-tracking data analyzed by The Associated Press corresponded with Iran’s description, showing a Gulfstream IV flown by Oman leaving Tehran’s Mehrabad International Airport just before noon. The plane landed just over two hours later in Muscat.

Jared Genser, a Washington-based lawyer representing the Namazi family, shared a photo of Namazi on the plane in a suit and tie.

“After a short layover, he will be leaving Oman and heading to Abu Dhabi,” Genser said.

In Abu Dhabi, Namazi will undergo a carotid endarterectomy at the local branch of the Cleveland Clinic to clear out a severe blockage to his left internal carotid artery, Genser said. That blockage put Namazi at high risk of a stroke.

Tehran said late Tuesday that Oman had thanked the Iranian government for “delivering” Namazi to Muscat. Oman and the U.S. did not immediately acknowledge the flight.

Namazi is a former UNICEF official who served as governor of Iran’s oil-rich Khuzestan province under the U.S.-backed shah. He was arrested in 2016, apparently drawn to Iran over fears about his incarcerated son detained in 2015.

Namazi was placed under house arrest for medical reasons in 2018 but prevented from leaving Iran despite his family’s pleas that he travel to receive emergency heart surgery after suffering multiple hospitalizations.

Last October, he underwent surgery in Iran to clear a blockage in an artery to the brain that his family and supporters described as life-threatening.

Security forces arrested his son, Siamak Namazi, an advocate of closer ties between Iran and the West, while he visiting Iran on a business trip.

Both Namazis were sentenced to 10 years in prison in Iran on what the U.S. and U.N. say were trumped-up spying charges.

The U.N.’s Working Group on Arbitrary Detention dismissed the cases against the two men, saying in 2017 their case is part of “an emerging pattern involving the arbitrary deprivation of liberty of dual nationals.”

“There is no evidence either Mr. S. Namazi or Mr. B. Namazi had a criminal record, including in relation to national security offenses,” their report read. “There is nothing to indicate that they have ever acted against the national interests of the Islamic Republic of Iran.”

AP