A California pastor has returned home after spending nearly two decades imprisoned in China.

David Lin, aged 68, was released and is now reunited with his family in the United States, the State Department confirmed Monday.

Lin, who frequently traveled to China in the 1990s to spread the Christian gospel, was detained in 2006 while assisting an underground church, according to China Aid, an advocacy group for persecuted religious activists in China.

In 2009, Lin was formally arrested on charges of contract fraud, a crime that he denied. After a court review, he was sentenced to life in prison.

Though he initially sought government permission to carry out his ministry work, it is unlikely he was ever granted official approval.

“We welcome David Lin’s release from prison in the People’s Republic of China. He has returned to the United States and now gets to see his family for the first time in nearly 20 years,” the State Department said in a statement.

The U.S. Commission on International Religious Freedom and advocacy groups have long claimed that the fraud charges were politically motivated.

Accusations are frequently used to target leaders of China’s house church movement, which operates outside state-sponsored religious organizations.

In China, all churches must be registered with the government and pledge loyalty to the ruling Communist Party.

Any unregistered church is considered an underground church, and its activities are deemed illegal.

Advocacy groups say Beijing’s crackdown on unregistered churches, and religious groups at large, has intensified in recent years.

“Those who participate in and lead house churches often face intimidation, harassment, arrest, and harsh sentences,” the U.S. religious freedom commission noted.

Although Lin’s original sentence was reduced, he had not been expected to be released until 2030.

His health had reportedly deteriorated during his time behind bars, raising concerns for his safety.

U.S. based nonprofit the Dui Hua Foundation have long been calling for his early release, citing poor prison conditions and Lin’s declining health.

They estimate there are more than 200 Americans under coercive measures in China.

The Chinese foreign ministry has not responded to requests for comment regarding Lin’s release, which comes after a visit to China by U.S. national security adviser Jake Sullivan.

Last month, Sullivan met with Chinese President Xi Jinping and other officials, with discussions aimed at reducing growing tensions between the two nations.

Lin’s release follows calls from U.S. lawmakers for the freedom of other Americans still detained in China.

Texas Republican Rep. Michael McCaul, chair of the House Foreign Affairs Committee, welcomed Lin’s release and urged the Chinese government to free Mark Swidan and Kai Li, two Americans still held on disputed charges.

Nelson Wells Jr. and Dawn Michelle Hunt are also imprisoned on drug-related charges and are considered “wrongfully detained” by Dui Hua.

Lin’s detention, McCaul said, “marks a rising trend of hostage diplomacy by authoritarians around the world.”

This article includes reporting from The Associated Press.