"We can confirm that a US Patent and Trademark Office employee, while traveling to China in a personal capacity, was made subject to an exit ban in China," a State Department spokesperson said.

"We are tracking this case very closely and are engaged with Chinese officials to resolve the situation as quickly as possible."

Beijing declined to discuss the case in detail. Foreign ministry spokesman Guo Jiakun told reporters, "China is a country under the rule of law, and it handles entry and exit affairs in accordance with the law."

The Washington Post, citing unnamed sources, said the man was a Chinese American who was visiting family and was stopped for not disclosing his work for the US government on his visa application.

In the final months of former president Joe Biden's term, China freed three jailed Americans in a swap. The United States in turn agreed to loosen its travel warning for China, encouraging Americans to "exercise caution" rather than discouraging travel.

While the Biden administration hailed its efforts to free detained US citizens, advocates say other Americans, generally dual nationals, are subject to exit bans on leaving China.

The United States earlier this month said it had arrested two Chinese nationals who allegedly sought to recruit US Navy servicepeople as intelligence assets.

President Donald Trump has described China as the top adversary of the United States but has also spoken fondly of his relationship with counterpart Xi Jinping.