A U.S. Navy helicopter ferrying passengers and cargo crashed into the Persian Gulf yesterday while trying to land on an American military command ship, killing one and leaving three others missing, according to military officials.

Five other men aboard the SH-3G Sea King helicopter were rescued from the water and are undergoing medical examination, said Air Force Lt. Col. Chuck Manker of the U.S. Central Command in Tampa, Fla.

Military officials said the helicopter was completing a "routine transit" from shore to the USS LaSalle in the central Persian Gulf and crashed while preparing to land on the ship in clear weather.

"There were no missiles, no sabotage," said one Pentagon official. "It was strictly an accident caused by pilot error or mechanical failure."

The crash, just a week after the reflagged Kuwaiti oil tanker Bridgeton struck a submerged mine and was damaged while under escort by U.S. Navy warships, renewed concerns about the consequences of the nation's expanding military operations in the gulf region, as the Iran-Iraq war rages in its seventh year.

"It doesn't help our case over there," said a Pentagon official. "It's one calamity after the next."

The accident came as U.S. diplomats in Western Europe, acting on new instructions from Washington, were formally asking five allied governments with naval capabilities to provide assistance in protecting gulf shipping from the threats of mines and other hazards.

Reports from London said U.S. Ambassador Charles H. Price requested British cooperation in a call on Foreign Secretary Geoffrey Howe. Officials said Price requested assistance of an unspecified number of mine-sweeping "assets" from the British fleet of 40 anti-mine vessels. No immediate response was reported.

Other nations being asked for help, administration sources said, are France, West Germany, Italy and the Netherlands. The gulf situation was believed to figure in Washington meetings yesterday of French Defense Minister Andre Giraud with Secretary of State George P. Shultz and Secretary of Defense Caspar W. Weinberger.

France and Iran broke diplomatic relations July 17, and the French have ordered the aircraft carrier Clemenceau to the region.

State Department officials said the discussions with allies encompassed potential military cooperation for dealing with future threats to shipping and political cooperation in the United Nations effort to obtain an Iran-Iraq ceasefire.

U.S. military officials said the Navy has begun an inquiry to determine the cause of the helicopter crash, which occurred at 5:58 p.m. (10:58 a.m. EDT) yesterday. Although officials refused to say where the helicopter had taken off, military officials familiar with the Persian Gulf operation said it most likely left Bahrain to fly to the LaSalle, command ship of the nine-vessel U.S. task force in the gulf.

The $11 million Sea King helicopter was not involved in mine-sweeping operations that began in the gulf after seven mines were detected off Farsi Island, near where the Bridgeton struck a mine U.S. officials believe was planted by Iran.

Weinberger has dispatched eight big RH-53D mine-sweeping helicopters to the gulf that are scheduled to begin operations there late next week.

The guided-missile destroyer USS Kidd, patrolling near the LaSalle when the Sea King crashed, launched a helicopter of its own, a Seasprite, which directed the rescue of survivors from the sinking aircraft.

The Kidd is one of three U.S. warships waiting to escort the Bridgeton and another reflagged Kuwaiti tanker, the Gas Prince, out of the gulf. Military officials said it is uncertain when the Bridgeton, which has been partially loaded with oil, will leave the port of Ahmid.

The Navy withheld identification of the crash victims pending notification of next of kin.

It was the third crash of a Sea King helicopter reported in recent months. Naval aviators said yesterday helicopter accidents often occur over water, where a featureless, reflecting surface can cause pilots to misjudge altitude. They said the heavy weight of engines atop the craft often cause it to flip upside down after hitting the water, making escape difficult.Karen DeYoung of the Washington Post Foreign Service contributed to this report.