A mid-level Romanian diplomat assigned to Washington drove his family onto an Army post in the Virginia suburbs early yesterday morning and pleaded for political asylum, State Department officials said yesterday.

Officials identified the defector as Nicolae Ion Horodinca, third secretary at the Romanian embassy, and declined to say what happened to him other than that his request for asylum was under review.

With his wife, Cristina, and their child in tow, the diplomat, said to be in his late 30's and facing orders to return up his Communist county today, pulled up at a Military Police post at Fort Belvoir around 1 a.m. Sunday and asked to be granted protection.

"There was a Romanian diplomat who requested asylum," said Susan Pittman, a State Department spokesman. "His case is under review. I'm not even going to answer questions that are remotely related to this case."

FBI and Immigration and Naturalization Service agents entered the case yesterday, but spokesman for both agencies and the Army declined to discuss the incident.

According to State Department records, the diplomat lived in Alexandria's Southern Towers complex, just off the Seminary Road exit of Shirley Highway. The apartments are located about ten miles north of the Fort Belvoir, a large Army base in Fairfax County.

A military spokesman at the post first maintained that the defection has not occured, but Pittmam later acknowledged that it had taken place there. According to one account, post MPs waited for more than an hour and a half after the diplomat's arrival before receiving instructions about what to do with him.

One State Department officials described Horodinca as a generalist. "He didn't deal with anything specific. (He dealt with) Economics, politics, people on the Hill, and diplomatic functions," the official said.