The U.S. missile cruiser that mistakenly shot down an Iranian jetliner departed Sunday for home port in the first American force reduction in the Persian Gulf since the Iran-Iraq cease-fire took effect.

France also began its planned naval cutbacks in the gulf region. British officials said a Royal Navy destroyer was badly damaged when it collided with a British cargo ship it was to escort.The USS Vincennes was officially detached from the Navy's Joint Task Force Middle East for a 13,000-mile voyage to San Diego, where it had been based until April, said U.S. sources in the gulf, speaking on condition of anonymity.

The Vincennes downed an Iranian A-300 Airbus on July 3, killing all 290 people aboard. It mistook the jet for an Iranian F-14 fighter. An official U.S. report blamed the tragedy on crew stress in a first-time combat situation.

The 9,600-ton warship, the first of the Navy's high-tech "Aegis" cruisers deployed in the gulf, was pulled out of the waterway after the disaster and operated in the Arabian Sea. Sources said the Vincennes would not be replaced, in effect reducing the U.S. fleet from 27 to 26 ships.

U.S. Navy sources said the Pentagon has given no timetable for cutbacks, and other U.S. warships are being replaced as planned.

In Washington, Pentagon spokesman Maj. Bill O'Connell said that as of 3:15 p.m. EDT the Vincennes "was still part of the Joint Task Force Middle East." He declined to say if the ship was preparing to leave or would be replaced because "we don't discuss operations of ships."

Hours before it was to sail, the Vincennes was one of several warships that responded to a distress call from the British destroyer Southampton after its collision with the freighter Tor Bay in the Gulf of Oman.

The 4,100-ton destroyer, with a gaping 9-foot hole in its port bow and its bridge crumpled by the impact, reached the United Arab Emirates port of Fujairah. Three crewmen were hospitalized with broken bones, naval sources said.

In Paris, the French Defense Ministry announced it was withdrawing the aircraft carrier Clemenceau and three other ships from its Indian Ocean fleet, which covers the gulf. The other vessels were the destroyer Du Chayla, the oiler Var and the Cantho, one of three French minehunters in the area.