The U.S. and Iran have conducted a prisoner exchange. The trade Saturday involves Chinese-American graduate student Xiyue Wang and Princeton scholar and Iranian scientist Massoud Soleimani. The exchange marks a rare diplomatic breakthrough between the two countries after months of tension.

Iran's foreign minister first announced the swap on Twitter. President Trump shortly after acknowledged Wang was free in a statement from the White House, saying he “is returning to the United States.” 

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

We thank our Swiss partners for their assistance in negotiating Mr. Wang’s release with Iran," said President Trump in a statement to NBC News

Hua Qu, the wife of Xiyue Wang, released a statement to The Associated Press saying “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. “We are thankful to everyone who helped make this happen.”

The exchange happened in Switzerland, where Wang, who had been detained in Tehran since 2016, was exchanged for Soloeimani, who was facing a federal trial in Georgia.  

Wang was arrested and sentenced to 10 years in prison in Iran for allegedly "infilitrating" the country and sending confidential material out. He was there conducting research on the Qajar dynasty.

Soleimani was arrested in the U.S. on charges he had violated trade sanctions by trying to bring biological material to Iran. 

Representatives for both Wang and Soleimani have maintained their innocence.

Iran has detained dual Iranian nationals and those with Western ties in the past to be used as bargaining chips, amid heightened tensions over its collapsing nuclear deal with world powers and sanctions.