US State Department says the employee was slapped with an exit ban while visiting the country in a ‘personal capacity’.

A United States government employee has been prevented from leaving China after visiting the country for personal reasons, Washington has said.

The employee of the US Patent and Trademark Office, an agency within the US Department of Commerce, was subject to an “exit ban” while travelling in China in a “personal capacity”, the US Department of State said on Monday.

“The Department of State has no higher priority than the safety and security of American citizens,” a State Department spokesperson said in a statement.

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

The statement comes after The Washington Post on Sunday reported that a Chinese-American man employed by the US Commerce Department was barred from leaving China after failing to disclose his work for the government on a visa application.

The report, which cited four unnamed people familiar with the matter, said the employee had travelled to China several months ago to visit family.

The Hong Kong-based South China Morning Post on Sunday reported that the man, a naturalised US citizen, was detained in Chengdu, Sichuan, in April over “actions Beijing deemed harmful to national security”.

The Post’s report cited an unnamed “source familiar with the matter”.

The Chinese Embassy in Washington, DC, referred Al Jazeera to remarks by Chinese Ministry of Foreign Affairs spokesperson Guo Jiakun, who on Monday told journalists he had “no details to share” on the case.

“China upholds the rule of law and handles entry and exit affairs in accordance with the law,” Guo said at a regular media briefing.

Washington’s confirmation of the exit ban comes after Beijing on Monday said it had blocked the departure of a US citizen employed by the banking giant Wells Fargo.

China’s Foreign Ministry said that Chenyue Mao, an Atlanta-based managing director, was subject to an exit ban due to her involvement in an unspecified criminal case.

Washington and Beijing have long traded accusations of espionage and meddling in each other’s domestic affairs.

On Monday, the US Department of Justice said that a Chinese-born US researcher had pleaded guilty to stealing trade secrets, including blueprints for infrared sensors designed to detect nuclear missile launches and track ballistic missiles.

Prosecutors said Chenguang Gong, a dual US-Chinese citizen, transferred more than 3,600 company files to his personal storage devices during his employment with a Los Angeles-based research and development firm.

Before taking up work with the company, Gong had travelled to China several times to seek funding to develop technology with military applications, prosecutors said.