Trump said Chinese-American Xiyue Wang was returning to the United States. An Iranian official said that Iranian Massoud Soleimani had been freed from detention in the United States.

Switzerland facilitated the swap and Iranian state news agency IRNA said Foreign Minister Mohammad Javad Zarif welcomed Soleimani in Zurich, where it said the swap took place. It said Soleimani was expected to return to Iran in the coming hours.

In a statement issued by the White House, Trump made no mention of the freeing of Soleimani but thanked the Swiss government for its help in negotiating Wang's release.

"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," he said.

Zarif said earlier the prisoner swap was imminent. Later he posted pictures on Twitter of himself with Soleimani talking on board an Iranian plane.

"Glad that Professor Massoud Soleimani and Mr. Xiyue Wang will be joining their families shortly. Many thanks to all engaged, particularly the Swiss government," Zarif tweeted.

IRNA reported that Wang was released based on "Islamic clemency".

Switzerland represents U.S. diplomatic interests in Iran since Washington and Tehran cut diplomatic ties shortly after the 1979 Islamic Revolution in Iran.

A U.S. official told the Associated Press that Brian Hook, the U.S. special representative for Iran, accompanied Soleimani to Switzerland to make the exchange and Hook and Wang were now "en route to Landstuhl in Germany where Wang will be examined by doctors".

It said Wang was expected to stay in Germany for several days. Landstuhl is home to an American military medical center.

U.S. Secretary of State Mike Pompeo said in a tweet that he was "pleased that the Iranian government has been constructive in this matter". He added, "we will not rest until we bring every American detained in Iran and around the world back home".

Three Long Years

Wang, a U.S. citizen and Princeton University graduate student, was conducting dissertation research in Iran in 2016 when he was detained and accused by Iran of "spying under the cover of research," an allegation his family and the university deny.

He was subsequently convicted on espionage charges and sentenced to 10 years in prison in 2017.

Hua Qu, Wang's wife, welcomed her husband's release.

"Our family is complete once again. Our son Shaofan and I have waited three long years for this day and it’s hard to express in words how excited we are to be reunited with Xiyue," she said in a statement.

"We are thankful to everyone who helped make this happen."

Soleimani, a stem cell expert, was arrested at Chicago airport in October 2018 for allegedly attempting to export biological materials to Iran in violation of U.S. sanctions on Iran over its nuclear program.

Washington has demanded that Iran release the Americans it is holding, including father and son Siamak and Baquer Namazi; Michael R. White, a Navy veteran imprisoned last year, and Robert Levinson, a former FBI agent missing since 2007.

Several dozen Iranians are being held in U.S. prisons, many of them for breaking sanctions.

Tensions have heightened between Iran and the United States since Trump last year pulled Washington out of a 2015 nuclear deal between Iran and six major powers and reimposed sanctions that have crippled Tehran's economy.

In return, Iran has gradually scaled back its commitments to the agreement.

REUTERS