Beijing — China on Monday called the expulsion of diplomats from the U.S. a "mistake," following reports that Washington quietly expelled two embassy officials in September after they drove onto a sensitive military base in Virginia.

The incident is the latest spat between the world's two biggest economies and comes days after they announced a truce in the form of a mini-deal to reduce some tariffs in a bruising trade war which has weighed on both sides.

Commenting on The New York Times report, foreign ministry spokesman Geng Shuang called the accusations "completely contrary to the facts" and said they "strongly urge the United States to correct its mistake."

Geng said Beijing had lodged "solemn representations and protests to the U.S." and called for Washington to "protect the legitimate rights and interests of Chinese diplomats."

The incident appeared to be the first time in more than 30 years that the U.S. has expelled Chinese diplomats on suspicion of espionage, the newspaper said Sunday, citing people familiar with the episode.

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At least one of the diplomats was believed to be an intelligence officer operating under cover, the Times said.

The Times said the diplomats, accompanied by their wives, drove up to the checkpoint at the entrance to a sensitive installation near Norfolk, Virginia that includes special operations forces.

The guard saw that they didn't have permission to enter and directed them to go through the gates, turn around and exit.

The Chinese officials continued onto the base, evading military personnel pursuing them until they were forced to stop by fire trucks blocking their path, according to the Times.

The Chinese officials said they had not understood the instructions they were given, but U.S. personnel were unconvinced by their explanation.

The motive for the incursion was not clear, but U.S. officials said they believe the Chinese diplomats were hoping to test the security measures at the base.

The two officials were expelled "this fall," the Times said. Neither country made the incident public, and Beijing apparently did not respond with tit-for-tat expulsions of U.S. diplomats in China.

The State Department did not immediately respond to AFP's request for comment on the report.

The United States and China remain at odds over a number of issues including industrial espionage, Beijing's presence in the South China Sea, and the situations in Hong Kong and Xinjiang.

Weeks after the incident at the Virginia base, the State Department placed restrictions on the activities of Chinese diplomats, in what it said was a response to years-old Chinese regulations limiting the movements of U.S. diplomats.

China instituted similar restrictions on U.S. diplomats in December. It is not clear if the restrictions were linked to the incident in Virginia.