A Chinese-born American seismologist who conducted US-funded research on detecting North Korean nuclear tests has been held in China for nearly two years and is facing trial on espionage charges, according to his wife, US lawmakers and two hostage advocacy groups.

The case of Youlin Chen has added another point of tension in US-China relations as President Donald Trump seeks to maintain stable ties with Beijing following last year’s trade dispute.

US Secretary of State Marco Rubio designated Chen, 54, as “wrongfully detained” on March 19, making his release a top US priority. His wife, Yufang Rong, said the Trump administration has avoided making the designation public to leave room for high-level diplomatic efforts to secure his release.

A US source familiar with the case said the administration was “focused on gaining his release from his unjustifiable detention.”

Chen, who became a US citizen in 2011 and lives in Boston, Massachusetts, is the only American currently held in China with a wrongful detention designation, according to his wife and hostage advocacy groups.

Rong said White House and State Department officials told her that Trump raised her husband’s detention with Chinese President Xi Jinping during a state visit to Beijing in May. She said Xi promised to look into the matter, but no action has followed.

The US source did not directly confirm that the issue was discussed. However, the source said Trump and Xi have a “very good personal relationship. This is one of many facets in the US-China relationship. No one issue is defining.”

Rong fears Chinese authorities have already decided the outcome of the case.

“I believe they will convict him no matter what and the trial will be behind closed doors,” said Rong, who is also a seismologist but does not collaborate on her husband’s work.

China rejected claims that Chen had been wrongfully detained.

China’s judicial organs handle cases according to the law and “there is no so-called wrongful detention,” foreign ministry spokesperson Lin Jian said.

The Foley Foundation, which tracks hostage cases, believes Chen is among at least 12 Americans being unjustly held in China, including individuals prevented from leaving the country.

White House deputy press secretary Anna Kelly said: “President Trump has been clear that he wants every American detained abroad to return home, and he has reunited over 100 individuals with their families since taking office this term.”

According to Rong, Chinese officials have questioned Chen more than 100 times about his research into the seismic signatures of North Korean nuclear tests.

Eric Lebson, a former US national security official advising Chen’s family, said he believes China is interested in Chen’s expertise to improve its ability to conceal underground nuclear weapons tests using a technique known as decoupling.

Lebson said Chen works for a US government contractor but has never held a US security clearance or carried out classified work. His research, funded by the US State Department and the Air Force Research Laboratory, was conducted with Chinese academics using publicly available Chinese data and remains accessible online.

A research paper Chen published in December 2020 examined the size of North Korea’s six known nuclear test explosions and methods for distinguishing their seismic signals from earthquakes. The paper stated it had been prepared for the US State Department’s arms control bureau and was “approved for public release.”

Human rights groups have argued that China’s state-secrets law allows authorities to classify previously public information as state secrets, exposing researchers and others to prosecution.

Chen was arrested by Chinese state security officers at Beijing International Airport on November 5, 2024, as he prepared to return to Boston after visiting family and delivering lectures at two universities.

Rong said her husband initially faced harsh detention conditions, including being forced to sit on a hard stool all day without being allowed to stand, read or exercise. She also said he was denied proper medication for diabetes and other health conditions.

She said Chen has since lost between 30 and 40 pounds because of poor nutrition and continues to receive inadequate medical treatment.

Chinese authorities formally charged him with espionage on May 1, 2025. He is yet to stand trial. The case is expected to feature during Xi’s planned visit to Washington in September.

US Senator Ed Markey said he remains “deeply concerned about Dr. Chen’s safety and wellbeing.”

“It is my hope that increased attention on his unjust detention will force the Chinese government to do the right thing and release Dr. Chen,” Markey said. (Arise News)