The shipment of Pershing II nuclear missiles to West Germany has been temporarily delayed to modify components of the weapon and the way it is assembled, U.S. and West German officials said today.

Missiles already deployed as well as their transporters will have to be modified, officials said. This will force limits on training but will not interfere with the limited number of Pershings on 24-hour operational alert, the officials said.

These actions, which U.S. officials said could mean delays of "a few weeks" in engine shipments and "months" of work on missiles already deployed, followed a U.S. Army investigation into the fatal fire of the motor stage of a Pershing II rocket at the Camp Red Leg Army base near Heilbronn, West Germany, on Jan. 11. Three U.S. soldiers were killed and 16 others were injured in the accident.

The motor, packed with solid fuel, was ignited by a charge of static electricity as it was being hoisted by a crane from its shipping container, according to an interim report presented today by U.S. Army Undersecretary James Ambrose to members of the West German Bundestag.

At least 54 Pershing II missiles are operational in West Germany, with some NATO sources putting the number of deployed rockets at 63. West Germany is scheduled to receive 108 of the fast and accurate Pershings by 1986.

Bonn's Defense Minister Manfred Woerner told the members of parliament that the United States had agreed "that no more rockets would be brought to West Germany until the modification has been completed," according to Alfred Biehle, the chairman of the Bundestag's defense committee.

Officials from the U.S. Embassy and West German Defense Ministry insisted, however, that the hiatus would not prevent the deployment schedule from being fulfilled by the end of the year.

Both governments are concerned that the accident and its aftermath could trigger renewed political controversy over the Pershings, which provoked massive demonstrations before deployment began in December 1983.

Woerner and Ambrose are expected to travel to Heilbronn Thursday to reassure the local population that there is nothing to fear from the presence of the missiles. The report insists that no nuclear warheads were near the scene of the accident and that at no time was the civilian population in danger.

The opposition Social Democrats contend that the Pershing II missiles were not adequately tested before being stationed in West Germany. The party's senior member on the defense committee, Erwin Horn, said today that the accident had created "a genuine sense of uncertainty" about the safety of the missiles.

The U.S. Army report calls for modifications to be made in the electrical and grounding systems of the rocket. The motor stage and its container also will have to be changed, as well as the assembly procedures.

All maneuvers involving the rockets, which are operated by the U.S. Army's 56th Field Artillery Brigade at three bases here, have been halted pending the missile overhaul.

A Defense Ministry spokesman, Capt. Ulrich Hundt, said it might be necessary to send the deployed missiles back to the United States to be modified, but U.S. officials said they believed that the required changes could be carried out in West Germany.

The U.S. Army report concluded that a static electric charge had built up as the soldiers made a second attempt to lift the missile from its container.

"The motor moved a few inches backward, and the rear end struck a steel brace inside the container. At that moment the motor ignited and burned," the report said.

Tests showed that a combination of low temperatures and low humidity made the rocket fuel more vulnerable to the accumulation of static electricity, Ambrose told the committee.

On the day of the accident, the temperature in Heilbronn was less than 20 degrees Fahrenheit, the report noted.

It said that four Pershing II motor stages had been unloaded safely in the same weather conditions shortly before the accident occurred and that the discharge of static electricity was "an extremely rare occurrence."