Three Americans who were detained in China have been released in a prisoner swap with Beijing, the Biden administration said on Wednesday. One of the men had been an F.B.I. informant, according to senior U.S. officials.

       John Leung, Kai Li and Mark Swidan were heading to the United States on Wednesday after months of diplomatic maneuvering to free them. Mr. Leung and Mr. Li had been held for three years and eight years. Mr. Swidan was held for more than a decade.

       “Soon they will return and be reunited with their families for the first time in many years,” said Sean Savett, a National Security Council spokesman. He said no other Americans are “wrongfully detained” in China, a designation that indicates that the U.S. government sees a person as the equivalent of a political hostage or that the charges are fabricated.

       In return, the United States released Xu Yanjun, a Chinese intelligence officer serving a 20-year sentence after he was arrested in Brussels in 2018 and extradited to the United States in a dramatic F.B.I. operation, according to two U.S. officials.

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       On Wednesday, Mr. Xu was listed in the Federal Bureau of Prisons system as “not in B.O.P. custody.”

       The exchange has been in the works, under intense secrecy, for months. During a global summit in Peru earlier this month, President Biden discussed a potential prisoner swap with Xi Jinping, the leader of China, in a meeting at Mr. Xi’s hotel.

       Hostage diplomacy has risen in recent years, as tensions between the United States and both China and Russia have grown. Those two superpowers increasingly see detaining U.S. citizens as a way to get back spies, arms dealers and others. The American government has warned U.S. citizens to reconsider travel to those countries or to be alert there.

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