Youlin Chen, a Chinese-born American seismologist, has been detained in China for more than two years and now faces trial on spying charges.
Chen's research focused on detecting nuclear testing by North Korea, and he has published work on the subject that was funded by the United States.
The detention has been reported by Chen's wife, U.S. lawmakers, and two hostage advocacy groups. The case adds a further irritant to the tense relationship between China and the U.S., coming at a time when President Donald Trump is seeking to keep the relationship steady.