RIYADH, SAUDI ARABIA, DEC. 2 -- Some U.S. field commanders, bracing for the possibility of going into combat with multinational forces that have never fought side by side, are warning of unresolved wartime command and communications problems that they say could lead to chaos and unnecessary casualties on the desert battlefield.

American military authorities say that without greater coordination and more joint maneuvers, many front-line Saudi and Arab troops -- some of whom use weapons and tanks identical to those of Iraq -- could be killed inadvertently by Americans when they are absorbed into U.S. lines in the initial hours of ground fighting.

In addition, U.S. military commanders say they need extensive training within American units to avoid a high rate of fratricide -- accidental killing of one's own troops -- in the expected massive confusion of combat in the air and on the ground.

The issue of military command and control, at the highest political levels as well as on the tactical battlefield, is one of the most controversial involving the coordination of the international force of more than 550,000 troops now assembling on the Arabian Peninsula. While Western and Arab political leaders have agreed to joint diplomatic control of the forces, many of the critical details of sharing a battlefield remain unresolved.

It is a topic so politically charged that many top-ranking military officials refuse to discuss it. Asked if U.S. commanders would have a serious problem with battlefield command and control among the multinational forces if ordered to war immediately, Army Maj. Gen. Paul R. Schwartz, who heads those efforts for American troops, responded: "No comment."

Brig. Gen. Granville Amos, assistant commander of the Marine air wing here, said, "I would rather not discuss it. The answer would benefit somebody else."

But some senior U.S. military officals and scores of field commanders, speaking without attribution, complain that political considerations and sensitivities frequently have outweighed military needs.

"It would be very difficult for the Saudis to say the U.S. will command all forces, even though that would be the best thing," a high-ranking American commander said. "So we're having to make do. Is it going to cost us American lives? No. We wouldn't stand for it."

In an effort to avoid some potential problems, Saudi and U.S. military leaders have carved Saudi Arabia's Eastern Province into slices, assigning each of the multinational forces sectors of responsibility.

"You try to keep everybody apart so everybody can contribute to the battle without shooting each other," a senior ground commander said. "It's not going to be very pretty."

Some senior U.S. officers have chafed under that structure, charging that the diplomatic concerns that require placing Arab forces on the Kuwaiti border have overridden military needs for having better-equipped American units closer.

U.S. officers say they also have been hampered in some coordination efforts by an international bureaucracy slow to organize joint military training. Saudi forces conducted their first large-scale ground exercise with American troops this weekend. U.S. Bradley Fighting Vehicles provided some support for the Saudi tank exercise.

The American military, by far the dominant force defending Saudi Arabia, has done little joint training with other military services and few large-scale maneuvers to test coordination among its own branches, according to officials in the region.

In the cluttered war room inside the modernistic Defense Ministry here, Saudi and U.S. military commanders sit side by side at computer terminals and maps, charting the daily buildup of forces on the Arabian Peninsula. In the morning and the evening, a senior Saudi and U.S. commander rotate in briefing the roomful of officers, as well as representatives from some of the two dozen other nations participating in the operation.

"We learn something new every day," Schwartz said, adding that "the biggest challenge is bringing it all together."

But in the desert, the lines of communication are not so clearly drawn nor are the liaison efforts between militaries so neatly arrayed.

Military commanders say a Middle East war involving American forces would likely be the most complex ever fought, with an invisible electronic war in the skies and a violent, complicated battle on the ground, with units from several nations using sophisticated artillery, tanks and missiles never before tried in combat.

Even after 40 years of coordination and joint exercises, NATO forces in Europe have been dogged by battlefield coordination and identification problems.

Military commanders say they face far more difficult problems attempting to coordinate a battlefield with forces that have not worked together, as well as militaries that use Soviet-made equipment that Western troops have long been trained to associate with the enemy.

Few American troops are training extensively with Arab or other forces and the joint programs now underway involve only basic skills, according to U.S. commanders participating in them.

U.S. Marines, the American troops closest to the Arab forces now lining the Kuwaiti border, have been training with small groups of Saudi forces for about three weeks. The troops are placing heavy emphasis on "passage of lines" -- movement of Saudi forces backward into U.S. lines as the American troops push forward to battle Iraqis.

"It is the most difficult combat maneuver there is," said Army Brig. Gen. Steven L. Arnold, the chief of plans and operations whose duties include training of U.S. forces on the Arabian Peninsula. "As they come back, we have to do a delay so we'll recognize them. . . . The confusion is obvious."

Saudi Arabia's small ground force -- fewer than 40,000 trained combat troops -- would not be considered a major player in any combat scenario, according to U.S. officials here. U.S. military officials, in the early days of Operation Desert Shield, estimated that Saudi forces would be able to withstand an attack from Iraqi troops for three to four hours before falling back into the American lines. When the U.S. Marine Corps staged a mock attack on a Saudi beach two weeks ago, only 34 of the 1,000 ground forces scheduled to participate were Saudis.

But the Saudi troops are regarded as critical to political considerations that Arab, and not Western, troops be the first to see combat in any war with Iraq, officials say.

Much of the desert training for American air and ground forces here has concentrated on identification of enemy equipment as well as the Soviet tanks and other weaponry being used by some nations that would be fighting alongside American forces. Commanders became so worried that U.S. Marines would have problems distinguishing between Soviet-made tanks being used by Iraq and by Syrian units in the multinational force that they recently abandoned plans to have the American and Syrian units side by side should fighting occur.

Those and other identification problems have prompted U.S. officials to devise new ways of identifying friendly and enemy forces, ranging from plans as simple as placing luminescent markings on friendly tanks to using sophisticated electronic identification systems.

"The coordination to make sure all of these things work is ongoing," said Marine Maj. Jim McClain, a spokesman for Marine aviation units in Saudi Arabia. "Is it going to be easy? No, it's not going to be easy."