U.S. military authorities yesterday ordered some additional naval forces to the Persian Gulf region, but said if President Bush ordered a major show of force or military confrontation with Iraqi forces in Kuwait, the U.S. military would need more than 45 days to fully mobilize and deploy to the Middle East.

An initial wave of Army airborne forces could arrive overnight and Marine assault units could arrive in the region within a week, but military authorities said those troops would be virtually useless against the Iraqi invading forces of more than 130,000 troops and 350 tanks that have seized control of Kuwait.

Military officials estimated yesterday that a U.S. counter-invasion force would require a commitment of up to 300,000 troops. This estimate was based on the total number of Iraqi combat troops available to fight in Kuwait on short notice.

"U.S. military operations would cease every place else in the world if we had to support any sizable operation in Kuwait," said a Pentagon official. "The effort for directing a ground confrontation would be enormous."

Although no large operations appeared imminent, Bush said yesterday he would not rule out the possibility of military intervention if Iraq does not withdraw its forces.

The military's crisis response team remained on alert last night in the National Military Command Center in the Pentagon. Senior officials considered or ordered these steps to increase U.S. military visibility in the gulf region:

The Navy ordered the attack aircraft carrier battle group led by the USS Independence to leave the Indian Ocean and make the three-day trip to the North Arabian Sea at the mouth of the gulf. The Navy has temporarily increased its Persian Gulf force from six to eight ships, keeping two warships in the region that had been scheduled to return to the United States after the recent arrival of their replacements.

A Marine amphibious group of four or five ships and the USS Saratoga attack carrier group are scheduled to leave their East Coast ports within a few days on routine deployments to relieve ships in the Mediterranean, but the ships they are scheduled to replace may be ordered to remain on station to increase presence in the region, officials said. Military authorities also were considering sending the USS Eisenhower carrier group deeper into the eastern Mediterranean closer to the Persian Gulf region, sources said.

Military planners are considering options to provide extra aircraft support to Kuwait's neighbors, including Saudi Arabia, if requested, officials said. The Air Force, which has already dispatched two extra aerial refueling tankers to the region, may send several more aircraft to support potential missions, according to officials.

The armed forces were preparing contingency plans yesterday to evacuate an estimated 3,800 American citizens from Kuwait if requested, sources said.

Beyond those efforts, military officials warned yesterday that despite efforts to upgrade U.S. contingency operations in recent years, the large-scale operation needed to respond to the takeover of Kuwait or any of its neighors would require a massive effort.

"It would be a logistical nightmare," one ranking Army official said. "We have no infrastructure in the region."

Most allies in the region have barred the United States from stationing more than token forces in their countries because of regional sensitivities. The U.S. Central Command, which directs all operations in the region, is located halfway across the globe in Tampa, Fla.

Even aircraft are hampered in their missions because many of the nations in the region refuse to give the United States overflight rights. Fighter jets and attack planes launched from an aircraft carrier outside the shallow Persian Gulf would barely have enough range to fly the circuitous routes to potential targets, officials said.

While some contingency forces could be airlifted to the region, most of the heavy artillery needed to combat the well-armed Iraqis would have to be shipped from the continental United States, which Army officials say could take 45 to 60 days.

In an effort to provide more rapid responses to military crises, the U.S. military has spent about $5.6 billion in the past decade to pre-position 25 civilian-operated cargo ships loaded with tanks, equipment and other supplies throughout the world. As a result of the 1979 Iranian hostage crisis and special problems of stationing troops and equipment in the Middle East, more than half of that force -- 14 ships -- is kept in the Indian Ocean within six steaming days of the Persian Gulf area, officials said.

The five pre-positioned Marine ships based at Diego Garcia deep in the Indian Ocean -- the squadron closest to the Middle East -- can sustain about 16,500 men with everything from bullets to beans for 30 days. About 52 M-60 tanks are available on those vessels. These would be only a small fraction of the forces needed to combat the Iraqi troops and armor now reported in Kuwait.

Most of the 300,000 troops and heavy armor needed would be loaded on ships on the East Coast for the 21-day trip to the Middle East. Once divisions on coastal bases were depleted, the Army would be required to move equipment by railroad from bases in Kansas and Colorado to the ports, requiring up to two months.

Military authorities said the special forces, airborne and light infantry units trained for rapid deployment throughout the world would be hardly a match for Iraqi armor and would likely take a high number of casualties.

Any large scale-effort would strain military operations worldwide, officials noted, citing the invasion of Panama. In the first critical nine days of the operation, the military used more than half of its active duty and reserve strategic airlift forces worldwide to deploy about 13,000 troops and supporting equipment to Panama, located only a fraction of the distance from U.S. bases as the Middle East.