WASHINGTON — A United States Army reservist from China was arrested Tuesday on allegations of secretly providing information about American defense contractor employees to a Chinese intelligence officer, law enforcement officials said. The Chinese government was trying to recruit them as informants, they said.

The suspect, Ji Chaoqun, 27, was arrested in Chicago, where he attended graduate school before joining the Army Reserves, and charged with violating the Foreign Agents Registration Act, or FARA.

Mr. Ji’s handler at a regional arm of China’s Ministry of State Security, which collects domestic and foreign intelligence, was also arrested, according to an F.B.I. affidavit. The officer, identified only as Intelligence Officer A, was arrested sometime before April. It is not clear where he was arrested or by whom.

An F.B.I. arrest of a Chinese intelligence officer would send a strong signal to China that American counterintelligence agents are keenly focused on its activities in the United States. Such an arrest would also be an embarrassment to Chinese intelligence, revealing sloppy tradecraft and exposing operations in the United States.