Dec. 7 (UPI) -- An American graduate student held in an Iranian prison for more than three years was freed Saturday in a prisoner swap involving an Iranian citizen being held in the United States on accusations of sanctions violations.
U.S. allies in Switzerland helped negotiate the release of Chinese-born, naturalized American citizen and fourth-year Princeton University doctoral student of history Xiyue Wang, 38, in exchange for Iranian citizen Massoud Soleimani, who has been held in Atlanta.
"Wang had been held under the pretense of espionage since August 2016," President Donald Trump said in a statement. "We thank our Swiss partners for their assistance in negotiating Mr. Wang's release with Iran.
"The highest priority of the United States is the safety and well-being of its citizens. Freeing Americans held captive is of vital importance to my administration, and we will continue to work hard to bring home all our citizens wrongfully held captive overseas."
Wang was researching Iran's Qajar dynasty in August 2016 when he was arrested, according to the university, his wife and the U.S. government. In April 2017, he was convicted of two counts of espionage and sentenced to 10 years in prison. He had been held in Evin Prison, which houses most of Iran's political prisoners.
In November 2017, Iran released a video of Wang allegedly trying to smuggle documents, but then-State Department spokesperson Heather Nauert denied he was working on behalf of any U.S. government agency.
Wang's wife, Qu Hua, told NBC News in November 2017 that he was struggling with depression in prison and she was trying to win his release. He had last seen his son when the boy was 2 years old.
"My son told his teacher that, 'When I grow up, my daddy will come home," she said at the time.
"Our family is complete once again," a statement from the family posted on Twitter Saturday said. "Our son Shaofan and I have waited three long years for this day and its hard to express in words how excited we are to be reunited with Xiyue. We are thankful to everyone who helped make this happen."
Soleimani is a medical research scientist whom the United States accused of violating sanctions against Iran by attempting to export biological materials in the form of human growth hormone without being authorized to do so.
"Glad that Professor Massoud Soleimani and Mr. Xiyue Wang will be joining their families shortly," Iranian Foreign Minister Mohammad Javad Zarif posted on Twitter. "Many thanks to all engaged, particularly the Swiss government."
The swap comes amid growing tensions between Iran and the United States after the Trump administration imposed sanctions and withdrew from the Iranian nuclear deal. Washington has also expressed support for Iranians protesting against Tehran over gas prices.
"America supports the brave people of Iran who are protesting for their freedom," Trump posted on Twitter.