DHAHRAN, SAUDI ARABIA, NOV. 10 -- The U.S. military, which already has stretched its supply lines rubberband-thin in Saudi Arabia, will face major logistical problems in nearly doubling its forces in the Persian Gulf region in the next two months, according to military officials.

Saudi ports, air bases and some key roads are clogged with supplies and equipment for the almost 240,000 troops here now, and U.S. commanders fear the bottlenecks will get much worse as the military prepares for an influx of up to 200,000 more troops.

The military is also worried about shortages of some items, ranging from desert combat boots and fatigues for troops to missiles for its new high-technology weapons systems. The Pentagon has been unable to keep up with the production demands for these items for the first deployment of forces, officials said.

"It will be a massive operation," said one military spokesman. "There will be serious problems and strains on the system."

Top military officials who recently visited Saudi Arabia, including Marine Commandant Gen. Alfred M. Gray Jr. and Army Chief of Staff Gen. Carl E. Vuono, were dismayed by inadequate supply lines to the forward-based combat units, according to officials who accompanied them on the tours.

"If the commanders are straight with you, they'll tell you that's going to be a major problem -- getting food, water and ammunition to the front lines," said U.S. Rep. John P. Murtha (D-Pa.), chairman of the House Appropriations defense subcommittee, after touring U.S. military units in Saudi Arabia today.

The U.S. military is now faced with supporting almost one-fourth of its entire forces and more than half of its combat strength worldwide in the Persian Gulf region. There will be more sailors, soldiers and airmen dedicated to Operation Desert Shield than have been defending Europe for the past 40 years and almost as many forces as were dispatched to Vietnam at the height of the war.

The new deployments ordered Thursday by President Bush will mean more than one half of the Navy's aircraft carrier battle groups -- six carriers with escorts and support ships, two battleships and other vessels totaling as many as 150 ships will be plying the Persian Gulf, northern Arabian Sea and Red Sea.

In addition, 75 percent of the Marine Corps' combat forces will be assigned to the region, as well as two-thirds of the Army's most potent heavy tank units.

Such a vast portion of the military has been ordered to the Middle East that Defense Secretary Richard B. Cheney has canceled plans to rotate desert-weary, homesick troops because there are not enough active-duty forces to replace them. That decision, coupled with political considerations and the mammoth task of supporting the forces, increases pressure to resolve the Persian Gulf crisis by late winter or early spring, according to many officials here.

U.S. Central Command Chief of Staff Maj. Gen. Robert B. Johnston described the initial deployment of 240,000 troops as "an operation of unbelievable magnitude" that "makes Vietnam look like kids' play in terms of volume" and pace.

Already, 132 ships have dumped more than 7.5 million tons of weapons, ammunition and equipment on the docks of Saudi Arabia and aircraft have flown more than 4,600 missions delivering more than 170,000 passengers and 159,000 tons of equipment to the kingdom, according to military reports.

Convoys of hundreds of trucks and other vehicles clog Saudi highways daily, moving troops, equipment and weapons to front-line positions. Sprawling base camps with mechanic shops, shower facilities and mess tents have sprung up across a desert floor formerly inhabited only by bedouins, camels and scorpions.

But three months after the first troops and equipment arrived on the Arabian peninsula, the military remains weeks away from establishing the forward desert supply bases that would be needed to support its troops in combat, officials said. Because military leaders put so much emphasis on dispatching combat troops into the region first, some major logisitics units needed to support those forces still have not arrived, officials said.

Pentagon officials also said the military does not have large enough stocks of ammunition for its more high-tech weapons, such as the Patriot air defense missile system, and has had to rush more missiles into production.

Military personnel from weapons repairmen to medical doctors are complaining that they are having problems obtaining some of the spare parts and equipment they need to run their operations. Marine mechanics at one Saudi supply depot said that while shiploads of some spare parts are en route to the Persian Gulf, they have been told that some material requested could take 100 days to reach Saudi Arabia.

Some Navy doctors based in field units that would be near the front lines say some of the medicines and supplies they have been provided are so out of date compared with what is commercially available that they have asked their home hospitals to send them additional equipment and drugs.

Maj. Gen. Gus Pagonis, who heads the Central Command's logistics operations here, said huge new supplies of spare parts and other support equipment have begun to arrive at Saudi Arabian ports but that his crews face major obstacles in moving the items to distant desert positions where troops are stationed.

The equipment must be sorted at the seaport or airport where it arrives, then be "delivered to units that are very far out in the desert where there are no roads," according to Pagonis. He said some of the equipment can "take days" to deliver to the field because of the vast distances and rugged terrain.

Much of the equipment remains at ports and other entry points because of a lack of transportation. One high-ranking Saudi official estimated that the multinational forces, including the Americans, need an additional 10,000 trucks and other vehicles just to support the troops now in the kingdom.

Pagonis and others say the logistics efforts have improved dramatically since the first chaotic days of the operation, when a 300-member crew worked 36-hour shifts to unload the planes that were landing every 10 minutes. Now, that logistics force has increased to 11,000 men and women, and aircraft flights have been reduced to less than one-third of their original numbers. Most of the weapons and equipment now arrive by sea.

Pagonis said the flight line and port dock operations have become far smoother in recent weeks.

Officials here and in Washington say it could be more than two months before all of the new troops arrive, giving Pagonis and other military officials time to organize supply operations for the troops now in place and to prepare for the arrival of the second wave of forces.

"We did it one time -- it'll be a lot easier the second time," Pagonis said.

"We're not beginning from a standing start," said Marge Holtz, spokewoman for the Military Sealift Command in Washington, which is responsible for all sea shipments to the region. "There's no learning curve; we've been here before."

Still the process of moving heavy armored divisions and Marine units by rail and truck to ports, loading them onto ships and transporting them halfway around the globe is a slow process. Once the weapons and equipment are rolled onto ships, the ocean journey from the east coast of the United States to the Persian Gulf averages 21 to 25 days. While the sea journey for the European-based forces that will move to Saudi Arabia will be cut to an average of 17 days, the logistics of moving them on land will be time-consuming, officials said.

Meanwhile, the tent cities and other facilities where new arrivals are housed while awaiting movement to the field are overtaxed and overcrowded. The rear base camp areas where hot, dirty troops from the field are allowed to rotate periodically for rest and relaxation are limited and cannot adequately accommodate the troops already here, much less an infusion of tens of thousands more, some officials note.

"I just don't know where they're going to put all these people," said one Army official.