Pentagon officials are preparing to send new contingents of special-operations forces to the Persian Gulf to help counter possible attacks from terrorists and suicide speedboat crews following new Iranian threats, military sources said yesterday.

Secretary of Defense Caspar W. Weinberger said yesterday he does not know how long the U.S. military buildup in the troubled Persian Gulf region will continue.

"As soon as you {stop}, some other anticipated risk may happen and everyone will say, 'But you didn't have enough resources,' " Weinberger told a breakfast meeting with reporters. "We try to put in the resources that deal with the requirements. That changes. That varies. I don't know when it will be enough."

Despite public assertions by Defense Department officials that Iranian threats are not "relevant to our operations" in the region, Pentagon sources yesterday said military leaders are scrambling to draw up new contingency plans to deal with the latest Iranian warnings after Friday's bloody demonstrations in Mecca.

Underscoring the sense of deep concern, Pentagon sources yesterday said U.S. intelligence sources detected what they believe to be a previously unknown Silkworm missile site in the final hours of Monday's escorting operation through the Strait of Hormuz, sending military officials into "a flurry for three or four hours."

U.S. Navy fighter planes flying above the convoy as part of its escort were ordered to activate radar-jamming devices against the possible Silkworm site, sources said.

Further investigation showed several missile launchers on truck beds had been positioned, but no active missiles or crews were detected at the site near Khuzistan, sources said.

"We had a false alarm," a Pentagon official said. "It was a case of being very careful with the potential Silkworm threat."

Adm. William J. Crowe Jr., chairman of the Joint Chiefs of Staff, went to the Pentagon at 3:30 a.m. Monday, sources said.

"He's in there frequently," one source said. "He hasn't had a good night's sleep in a long time."

The decision to send several additional teams of the military's elite antiterrorist and unconventional warfare units to the gulf comes amid bitter debates among the military services over the embarrassing July 24 incident in which a submerged mine blew a hole in the supertanker Bridgeton during the first U.S. Navy convoy of reflagged Kuwaiti oil tankers. A minefield was later discovered in the area.

The Iranians began three days of military maneuvers, dubbed "Martyrdom," in the gulf yesterday, and warned all foreign vessels and aircraft to stay away from Iranian territorial waters and airspace in the Strait of Hormuz.

"There's no change in our plans for operations in the Persian Gulf, the Indian Ocean and that general area," Pentagon spokesman Robert B. Sims said yesterday. "We don't accept the threats or other claims of specific closures as being relevant to our operations, and so we will continue to carry out our mission there."

But one Pentagon official said, "Everybody's wary just of the sheer fanaticism" of the Iranians.

Although congressional sources said the second U.S. Navy escort of three American-flagged Kuwaiti tankers through the Strait of Hormuz and northward toward Kuwaiti oil ports in the upper gulf is scheduled to begin Thursday, Pentagon officials yesterday declined to say when the convoy would start. They noted that a delay would give the United States time to strengthen forces to deal with threats from mines and speedboats. The Bridgeton is still undergoing repairs and may not be moved for several more days, officials said.

Pentagon sources said several high-speed patrol boats were loaded onto the USS Raleigh, an amphibious transport ship carrying four small mine-sweeping vessels to the gulf. The Raleigh left Charleston, S.C., yesterday morning and is not scheduled to reach the gulf for about a month.

The patrol boats, about 65 feet long and weighing 30 1/2 tons, plus 9 1/2 tons of weapons and equipment, are armed with a 40 mm rapid-fire bow gun and can be fitted with several 20 mm rapid-fire guns or machine guns. The craft, with six-man crews from the Navy's elite Seal teams, have a top speed of about 40 mph.

Although the Iranians have several dozen Swedish-built patrol boats that can reach 60 mph and may be armed with heavy-caliber recoilless cannon, Pentagon officials say the Navy's patrol craft and helicopters are capable of dealing with any speedboat threat.