LONDON, OCT. 31 -- Senior British defense sources said today that any military operation to oust Iraqi troops from Kuwait would have to include attacks on air bases inside Iraq to establish the air superiority crucial to victory.

Briefing American reporters here, the sources said the first priority in case of war would be to destroy Iraq's air force, give allied forces control of the air and thereby neutralize Iraq's large advantage in ground troops and tanks.

Any hope of limiting the fighting to Kuwaiti territory was unrealistic, they indicated, and would leave allied ground forces with the difficult task of breaking through the Iraqi army's elaborate defenses inside Kuwait without unchallenged air support. But they conceded that attacks on airstrips, ground-to-air missile batteries and other military installations inside Iraq would cause casualties among the Western hostages whom Iraqi President Saddam Hussein has ordered placed at those sites.

The remarks came on a day when the British government, like that of the United States, appeared to be preparing its public for the likelihood of war in the Persian Gulf. The commander of British forces in the gulf said in a separate briefing here that they would be ready in about two weeks to participate in an offensive operation against Iraq.

"I can only guess at the outcome," said Air Chief Marshal Sir Patrick Hine. "It is looking increasingly unlikely that Saddam Hussein will withdraw unconditionally from Kuwait."

Britain has committed about 16,000 troops and support staff, including the 7th Armored Brigade, which has 9,500 troops and 120 tanks, plus more than 40 combat aircraft and 12 ships. But until now, officials have been reluctant to discuss openly how they would fight a war in which they would largely be following orders and battle concepts dictated by the much larger U.S. contingent.

The defense sources generally painted a cautious, even pessimistic portrait that emphasized the uncertainties and difficulties of a confrontation with the well-equipped and -fortified 390,000 Iraqi soldiers they estimated are deployed in the "Kuwait theater" -- stretching from Basra south through the oil sheikdom.

"One thing we are clear about is it's not going to be a cheap business in terms of casualties," said a high-ranking defense source.

Sheer numbers suggested part of the problem, they said. By mid-November, they projected, allied forces will have about 1,600 tanks, compared to the 3,600 they said Iraq has deployed in the likely combat zone. Iraq will have 2,300 heavy guns compared to only 750 for the allies, by this account. But the allies expect to have an advantage of 1,110 to 800 in combat aircraft, and 310 to 125 in attack helicopters.

Air power seems to be Iraq's main point of vulnerability, they indicated. While many of its aircraft are modern and sophisticated, many others are not, they said, and all operate under a rigid command and control system.

One source said, "We think the air battle will be the key to any conflict and the balance of the battle should be to the allied side."

The sources said they hoped the destruction of Iraq's air force could be achieved "in several days." The next step, they said, would be to reduce the Iraqi advantage in tanks, but that would be difficult if they remained in the heavily fortified positions most currently occupy along the Kuwaiti border with Saudi Arabia and in two backup defense lines.

Unlike allied commanders in Saudi Arabia, the defense sources here refused to predict that an allied offensive would succeed. "I don't think we would get involved in a military operation unless we had that confidence," said one. "Whether we have that confidence yet is an open question."

They also refused to discuss the prospect of an amphibious landing in Kuwait, but confirmed that allied troops have been conducting training exercises for such an operation and said Iraq has deployed four or five divisions along the coast to defend against such an attack.

They cited several other factors as important to the success of a military attack, including the participation of Arab troops and the impact of economic sanctions on the food supply, equipment and morale of Iraqi forces.

Such factors might be critical in deciding how long Iraqi forces would hold out once their air support had been destroyed, the sources indicated. That in turn could determine whether the conflict would be ended quickly or drag on. "We would be trying to make it as short a conflict as possible," one source said.