Defense Department officials said yesterday that Soviet troops in East Germany deliberately bumped a U.S. military vehicle on duty there Sept. 7 and detained two U.S. soldiers in it at gunpoint for up to nine hours before releasing them unharmed.

The Americans involved were members of the same liaison unit as U.S. Army Maj. Arthur D. Nicholson Jr., who was shot and killed by a Soviet sentry March 24 while trying to photograph Soviet military equipment in a garage-like storage shed near Ludwigslust, about 100 miles northwest of Berlin.

Defense Secretary Caspar W. Weinberger confirmed the latest incident -- the fourth this year between Soviet troops and U.S. or British soldiers -- in a television appearance in which he sharply criticized the alleged treatment of the Americans.

Weinberger referred to only one person, but Pentagon officials said two Americans, both unarmed, were in the "truck-like" U.S. vehicle, which was leaving a Soviet communications site in the southwestern corner of East Germany. Neither U.S. soldier was identified.

"The Soviets bumped his truck deliberately when we were where we were supposed to be and doing what we are permitted to do under a treaty that's some 40 years old," Weinberger said on CBS-TV's "Face the Nation."

"When he attempted to get out to fix the truck, they pushed him back into the truck and held him at gunpoint, detained him for roughly nine hours and generally behaved in the same way which they did in the incident in which Maj. Nicholson was killed and murdered," Weinberger said.

The United States has protested the action to Soviet authorities but has not received "anything very positive" in response, Weinberger said.

The Nicholson incident, which President Reagan termed an "unwarranted tragedy," sparked a long and bitter exchange between U.S. and Soviet officials, including U.S. demands for an apology and compensation for Nicholson's family.

An assistant military attache at the Soviet Embassy here was expelled in the wake of the controversy, and the United States took no official part in some World War II commemorative observances involving Soviets.

Weinberger said yesterday, however, that he did not think that the latest incident would affect Reagan's scheduled summit meeting in Geneva Nov. 19-20 with Soviet leader Mikhail Gorbachev. "You just have to recognize that this is Soviet behavior," the secretary said. A White House spokesman had no immediate response yesterday.

In response to a question about why the incident was not announced shortly after it occurred, Weinberger said, "We're trying our best to get the condition corrected. We aren't interested in publicity." He said the administration was not trying to keep the incident quiet.

Weinberger said that after the Nicholson incident, top Soviet military officials in East Germany had said they would "tell their people not to use force, and either they're not keeping those promises or they have a very poorly disciplined unit."

The "promises" to which Weinberger referred have been disputed by Soviet leaders. They have insisted that in meetings following the Nicholson incident they have not "renounced the right to take legitimate steps provided for by the military manuals," as reported by State Department officials.

They contend that at the time of his death, Nicholson was operating outside the bounds of the 1947 accords that allow each side access to the other side's occupation area, and was shot because he was an "unknown intruder."

The accords, set up at the close of World War II by the four Allied powers, allow each side to have an outpost manned by up to 14 members and conduct surveillance activities sometimes described as "licensed espionage." The U.S. operation is based in Potsdam in East Germany, just outside Berlin.

Defense Department spokesman Robert B. Sims said yesterday that the Sept. 7 incident occurred at about midday German local time as the U.S. vehicle attempted to leave a Soviet communications site in the Suhl area, about 100 miles southwest of Leipzig. The U.S. vehicle was not in a restricted area, Sims said.

The U.S. vehicle "became entangled or stuck. That's when the ramming or grazing or whatever the Soviet truck did occurred . . . . When it became immobile, the Soviet truck approached at a high rate of speed and hit our vehicle," Sims said. "Then Soviet soldiers surrounded it, directing our people to remain inside."

Later, the Soviets towed the immobilized American vehicle to another site and photographed it. It was subsequently returned to the custody of the Americans, who spent two hours repairing it and then left, Sims said. The nine hours referred to by Weinberger may have included the repair time, he said.

The incident was the second involving the two military missions since the one in which Nicholson was killed. On July 13, Col. Roland Lajoie, the commander of the U.S. unit, was injured when his car was rammed from behind by a Soviet vehicle near Satzkorn, outside Berlin.

The Associated Press quoted an unnamed administration source as saying it was unclear if the U.S. vehicle "was in a place it was supposed to be," and that a Soviet commander who came to the scene had "apologized profusely" for the latest incident. Weinberger may have "overdramatized what happened," the AP report quoted the source as saying.

Sims told The Washington Post in response that he knew of no such apology and that it had taken six hours "for someone in authority" to get to the scene. "It sounds as if they're a bit mixed up," Sims said of the source's comments.

In his television appearance yesterday, Weinberger also said, "I don't think the president has any intention of making the Strategic Defense Initiative a bargaining chip" in arms control talks with the Soviet Union.

This came in response to a question concerning a possible agreement under which the Soviets would make deep reductions in their strategic weapons and missiles in return for a U.S. compromise on the defense initiative, a satellite-based anti-missile program.

"The president has put before the world the most hopeful concept that mankind has seen, and that is the Strategic Defense Initiative . . . . It is vital that we continue this work," Weinberger said. "The president, to the best of my knowledge, has no intention of taking away from mankind this hope that he has placed before them."