The United States should face up to the possibility of losing thousands of lives in vain to protect Middle East oil, the four-star general in charge of contingency planning here said in an interview.

Army Gen. Volney F. Warner, commander of the U.S. Readiness Command and overseer of the Rapid Deployment Force headquartered at the edge of this base in Tampa, added that the 82nd Airborne Division and a Marine brigade would not be "too big a force to lose" to make a stand in the Persian Gulf.

The 82nd and a Marine brigade, a force of about 35,000 men, represent as large an outfit as the United States would be able to deploy to the Persian Gulf within 21 days and keep supplied, he said. Not until around 1985, Warner added, would there be enough extra cargo ships and planes to rush a force big enough to match the 80,000-man expeditionary force the Soviets have sent into Afghanistan on Iran's northern border.

If those Soviets troops threaten to close the Strait of Hormuz, the choke point for oil tankers steaming into and out of the Persian Gulf, Warner warned, civilian leaders may have to send in a force too small to stop them.

"It's a hell of a thing, maybe, to say," Warner continued, "but that's kind of what we ought to think about. We don't always commit with a 100 percent guarantee we're going to win."

Warner's assessment of the risks in backing up President Carter's pledge in his State of the Union address to go to war if necessary to keep "any outside force" from controlling the Persian Gulf is the grimmist yet given publicly by a top-ranking military leader directly involved with contingency planning.

The general's view is shared by many other military professionals, even through their civilian boss, Defense Secretary Harold Brown, is stressing how much more the U.S. military is doing and can do in the Persian Gulf today than in previous administrations.

Such contrasting portraits aside, the military realities seen through Warner's end of the telescope explain why generals and admirals are not spoiling for a fight in the Persian Gulf region. The mismatch between U.S. and Soviet capabilities there also is why at least one Pentagon civilian has raised the possibility of resorting to nuclear weapons to stop a big Soviet thrust to the oil fields in southern Iran.

Warner stressed in the interview that he was not shying away from committing U.S. forces to a place like Iran in an attempt to deter the Soviets from making a grab for the oil. Quite the contrary, he said, making such a stand might someday be in the national interest, even if it was known in advance that the American troops would lose if shooting started.

"Even if I knew the Marines couldn't win, the 82nd couldn't win," said Warner, "if there were a threat to Hormuz or something of that nature that was deemed serious enough, I'd be the first one to go.

"It wouldn't bother me at all, because I still think that the reason that people in the military are different from civilians is that in peacetime they're sworn to defend the country, and, if need be, to die for it.

"And if somebody says we've got to commit the 82nd or that Marine brigade right now -- it's in the national interest -- that's not too big a force to lose."

Assuming the Soviets were considering moving troops south through Iran to control the Strait of Hormuz, Warner continued, sending the 82nd and Marines to a blocking position would be saying to the Soviets: "OK guys, if you do, that's going to be a big bump, because we're in the area and all that implies when you bump up against the United States."

Because the United States will become increasingly vulnerable between now and 1985 when more airlift and sealift capabilities are available, "I would be more inclined to do it now than later," said the general of taking a stand in the Persian Gulf against a Soviet threat.

Warner conceded that if an inferior American force should fail to deter the Soviets from moving on Persian Gulf oil fields the United States would be "in a hell of a shape."

Asked if the loss of the 82nd Airborne in such a confrontation would not trigger World War III as the American people demanded revenge, Warner replied:

"I'm not sure. They might say, 'Let's go drown the Soviet brigade in Cuba.' I'm not sure what they would say, but I'd rather run that risk than not respond and let it [a Soviet thrust to control the Strait of Hormuz,] happen. That's the worst perception."

While Warner sounds grim warnings about the limitations of the Rapid Deployment Force that President Carter is counting on to handle trouble in the Persian Gulf, the day-in-and-day-out commander of that outfit projects optimism.

Marine Lt. Gen. P. X. Kelly, commander of the RDF, tells a visitor to his headquarters at the edge of a swamp, where snowy egrets feed leisurely as if war is nothing to worry about, that his outfit is pretty good now and getting better.

In peacetime, Kelly is a three-star general reporting to the four-star Warner. In wartime, he would still be a three-star general but would report to the Joint Chiefs of Staff, which theoretically would empower him to give orders to four-star generals.

If all the existing military units that could be assigned to Kelly in a war were assembled, he would be commanding more than 200,000 troops. The possibility of that happening has prompted the Joint Chiefs to consider making the head of the RDF a four-star theater commander.

While Kelly acknowledges that a fourth star would help the RDF commander in the real life of the military, he insists that all four services have put aside traditional rivalries and helped his headquarters staff figure out ways to handle the problems looming in the Persian Gulf. The RDF headquarters was established here on March 1, 1980.

His job is to figure out what can be done with forces now available and draft detailed plans to do it. He must prepare for a come-as-you-are war because the RDF cannot count on launching from nearby bases.

"Wherever we go," said Kelly, "we start with zero combat power on the ground till the first guy with a rifle gets there. Then we start the incremental buildup.

"You've got to have a balance, not only a guy who can pull the trigger, but a guy right behind him to provide the bullets and the chow. It all has to come in a very well-orchestrated way. You just can't have the airplanes come in first, or the people come in first. You have to have it all come in sequentially in an integrated way."

A rough parallel in civilian life would be to load a moving van for a run from Washington to Los Angeles, throw a dinner for 50 in the house two hours after arriving -- and then have everybody stay overnight.

Except for Marine amphibious landings, said Kelly, the U.S. military has not had much experience in fighting with what the troops bring along. They fan out from bases rich in supplies in most cases, even in a jungle war like Vietnam.

"What I can do today that I couldn't do six months ago," said Kelly in claiming significant strides for his headquarters, "is that I can tell you essentially what my real world capabilites are in terms not only of people and equipment but also in terms of logistics sustainability" -- the beans and bullets for the troops.

He rejected charges that the RDF is just a political gimmick, a paper army. Thanks, to detailed planning already accomplished here, said Kelly, the 82nd Airborne could be deployed to the Persian Gulf and sustained there within two weeks. He agreed the RDF is short of ships and cargo planes needed to land and support a large force.

He declined to discuss how and where the RDF might be likely to go in the future, stressing the outfit is designed to go into a country only when it is invited.

Asked what his biggest problem is in surveying the whole landscape confronting the RDF, Kelly gave a oneword answer: "Distance."