Defense Secretary Caspar W. Weinberger said yesterday that it will be "quite a long, cold winter" before the United States can reduce its military buildup in the Persian Gulf.

But the nation's top military leader, Adm. William J. Crowe Jr., chairman of the Joint Chiefs of Staff, told a Senate committee that the Navy is looking for ways to cut back its force there.

Underscoring Weinberger's forecast, Defense Department sources said the Pentagon has leased two commercial barges as gulf operations bases for small mine-sweeping vessels and Navy commando speedboats.

This was done despite concern expressed by senior naval leaders that the barges could be vulnerable to terrorist attack, the sources said.

Meanwhile, the Senate, frustrated over President Reagan's refusal to involve Congress in gulf decision-making, voted, 98 to 0, to ban Iranian imports ranging from crude oil to rugs and pistachio nuts. {Details on Page A23.}

Weinberger, after returning from a five-day visit to the gulf region, said on ABC's "Good Morning America" that U.S. military operations "will be required until the Iranians change their behavior, and I'm afraid that's going to be quite a long, cold winter until that's happened."

Crowe told the Senate Armed Services Committee, "We are looking at ways to draw down our forces to a more reasonable level."

Withdrawing all U.S. forces from the gulf, however, would be a "terrible error and admission of incapability," he said. Thirty warships and about 15 smaller mine-sweeping and Navy commando boats are in the region or heading there.

The Pentagon announced that the guided-missile frigate USS Hawes began escorting a reflagged Kuwaiti tanker through the Persian Gulf about 10 p.m. EDT Monday, the 10th such convoy since late July. Officials said the U.S. warship and the liquefied-gas carrier, the Gas Prince, were "proceeding uneventfully in the central Persian Gulf."

Officials also said they are uncertain whether the Navy has located a small mine field about 15 miles north of Dubai. The crew of the USS Kidd reported sighting what it believed to be mines bobbing in the water Sunday.

U.S. military sources here and in the gulf have said Navy crews believe that they have identified five mines and are warning commercial and military vessels to avoid the location.

British Royal Navy mine sweepers that have joined U.S. forces in the mine-hunting effort spotted a "suspected mine" in the area yesterday, according to shipping sources.

Pentagon sources also said the United States is monitoring two Iranian vessels suspected of being potential mine-layers.

Weinberger said U.S. forces, in some situations, may attack suspected mine-layers before weapons are dropped overboard. Last week Army helicopters fired machine guns and rockets at the Iran Ajr after they spotted its crew putting mines in the water.

"When there is a hostile act committed, we don't have to wait for anything more to go and take appropriate action," Weinberger told Cable News Network yesterday. "The same is true when hostile intent is discovered. That's a little harder perhaps to determine . . . . "

The large leased commercial barges are being used as bases for small Navy mine-hunting and SEAL {sea-air-land} special-operations teams, Pentagon sources said.

"We've had to resort to floating barges because we're unable to get the necessary pier space ashore to support our mine-sweeping vessels and other craft," a Pentagon official said.

Pentagon sources said some senior naval leaders have expressed concern that the barges could easily become terrorists' targets. Sources said the barges, about 100 feet by 400 feet, are protected by commando speedboats armed with machine "When there is a hostile act committed, we don't have to wait for anything more to go and take appropriate action."

Caspar W. Weinberger

guns. Sources said some light weapons, possibly Stinger ground-to-air missiles, may be used on the barges for protection.

"It's capable of defending itself," one Pentagon official said.

The barges contain sleeping accommodations for repair and maintenance crews and storage for spare parts and fuel, sources said.

They said the barges, one of which is moored off the coast of Bahrain, "look like a commercial rig." One Pentagon official said some military leaders have said they fear that the barges may not be seaworthy enough for use as naval-operations platforms.

In other gulf developments, the Koriana, a Greek tanker, was attacked by an Iranian gunboat about 90 miles west of Dubai, according to the insurance firm Lloyd's of London. The ship's captain reported no injuries in the attack.