Marine Lt. Col. William Richard (Rich) Higgins, kidnaped by gunmen in Lebanon yesterday, "actively sought" the post with the U.N. observation unit he heads in that country, according to Pentagon officials.

Higgins, 43, lived in Woodbridge when he was assigned last June to the Lebanon Observer Group, part of the U.N. Truce Supervision Organization that operates throughout the Middle East, Pentagon officials said. Last month, he became chief of the 75-member Lebanon unit, which includes 16 U.S. military officers, officials said.

Pentagon and State Department officials said yesterday that Higgins' kidnaping has not triggered discussions about removing the remaining U.S. team members from Lebanon.

"These people are not assigned as a national contingent," said State Department spokesman Charles E. Redman. "There are U.S. officers assigned to this organization, and as such, they are under the authority and responsibility of this {U.N.} organization."

Some Pentagon officials expressed concern over the vulnerability of U.S. troops serving in Lebanon, noting that the State Department has recommended for the past several years that American civilians leave that country.

But other military officials noted that the United States has participated in the U.N. unit since it was formed in 1948 and did not withdraw its members even after the 1983 bombing of the Beirut Marine barracks, in which 241 Marines and other U.S. personnel died.

The Lebanon Observer Group operates six observation posts and conducts patrols along the Lebanese-Israeli border in conjunction with the United Nations Interim Force in Lebanon (UNIFIL), created after the March 1978 Israeli invasion of Lebanon.

A Norwegian television correspondent who traveled with Higgins through southern Lebanon two weeks ago told CBS News, "He was aware of the risk. He said, 'We can be kidnaped. We can be shot at. We can be robbed. But this is a part of our daily life.' "

The Norwegian journalist said Higgins traveled with him without an escort or weapons. He also said Higgins expressed a special interest in the pro-Iranian Hezbollah and reports that the group was increasing its activities in the area. "He was eager to find out how strong they were," the reporter said.

Higgins became chief of the unit in January as part of an agreement in which the U.S. senior military observer serves as commander from January to June of each year and an Australian lieutenant colonel heads the group for the rest of the year. His one-year tour in Lebanon began last June.

The United States has assigned 36 military officers to U.N. observer groups throughout the Middle East, including the 16 in Lebanon. Ten are in Egypt, seven are in Jerusalem and Tiberias in Israel and three are in Damascus. They represent all branches of the U.S. armed forces.

The 36 U.S. officers are among 299 troops from 17 nations, including the Soviet Union, that participate in the observer groups.

Higgins joined the Marine Corps in 1967 and served in the infantry in Vietnam. He was awarded the Defense Superior Service Medal and the Bronze Star. He has served in various command positions and was promoted to lieutenant colonel in January 1983.

Higgins "actively sought" an assignment with the U.N. unit in Lebanon after several years of duty in the Washington area, according to one Pentagon official.

His wife, Marine Maj. Robin Higgins, works in the Pentagon's public affairs office. She was informed of her husband's disappearance at about 9 a.m. yesterday. She was interrupted in a routine staff meeting by a telephone call from the State Department.

A family friend drove the couple's daughter, Chrissy, 17, to the Pentagon from Woodbridge yesterday morning so that her mother could relay the sketchy details of her father's disappearance, according to a Pentagon colleague. The Higgins family has lived in Woodbridge for the past 1 1/2 years, the coworker said.