U.S. military officials expressed growing frustration yesterday over the difficulty of assessing the effectiveness of the air war in the Persian Gulf, while Iraqi threats to move captured allied pilots to strategic sites drew angry warnings from President Bush and others against any mistreatment of prisoners of war.

Bush, arriving at the White House after a weekend at Camp David, denounced the "brutal parading" of the pilots on television by the Iraqis, calling it a "direct violation" of the Geneva Conventions that protect POWs. "America is angry about this, and I think the rest of the world is," the president said.

Military officials offered a somewhat more guarded picture of the progress of the Persian Gulf War so far, acknowledging continued difficulty in eliminating the Iraqi Scud missile threat to Israel and Saudi Arabia and blocking the ability of Iraqi commanders to communicate with their troops. Thick cloud cover remained a problem, hampering bombing runs and limiting efforts at damage assessment by the Pentagon.

"There's frustration level all over the building about what bomb damage assessment is," Pentagon spokesman Pete Williams said yesterday. Reporters pressed Williams and other Pentagon officials to explain how the military could continue to claim a high degree of success in the early stages of the war without providing a more complete picture of the damage to Iraq's military. Williams added: "There is a great desire all throughout the Department of Defense, not just here in the briefing room, to have a clearer picture of bomb damage assessment."

Defense Secretary Richard B. Cheney said the air war has gone "about as expected," with fewer allied casualties than feared. But Cheney, noting that U.S. officials never believed the allied forces could eliminate Iraqi President Saddam Hussein's military machine in a matter of days, said that despite early successes, the length of the war "could conceivably be weeks, could conceivably be months."

Military officials said Iraqi planes continued to offer little resistance, and they expressed confidence in the allies' ability to control the skies. The coalition forces listed 14 aircraft lost to hostile fire, including nine U.S. planes, though a military official said the Pentagon was delaying word of additional downed aircraft in order to give search teams time to attempt rescues without tipping Iraqi forces. Fourteen American airmen were listed as missing in action.

Responding to a statement from Saddam on Sunday that he is husbanding his resources and intentionally keeping much military might in reserve, Cheney said the Iraqi air force has been "almost totally ineffective," while Saddam's ground forces "haven't displayed any offensive capability since they took Kuwait last August."

But the diminished flow of information from the Pentagon and the U.S. Central Command in Riyadh, Saudi Arabia, complicated assessments of how much remains to be done before a ground war may be launched.

Among the things still not known with precision are: the damage done to the capabilities of Iraqi ground forces under heavy bombardment; the number of remaining Iraqi airplanes, many of which have been sheltered; and the extent of damage to Saddam's command-and-control system, a top priority of the air campaign.

Officials blamed uncertainty as well as a need for military secrecy for the paucity of information. Asked yesterday whether he would answer several questions about the impact of the war to date, Lt. Gen. Thomas Kelly, senior operations officer for the Joint Chiefs of Staff, said, "The short answer is no."

A military official said Iraq launched six Scuds at Saudi Arabia late yesterday and early today. The first landed in the sea; two others were intercepted by U.S. Patriot air-defense missiles; two were allowed to fall harmlessly in the desert, and information was still being collected on one, Lt. Col. Greg Pipin told a briefing in Riyadh.

U.S. officers briefing reporters on the course of the war said they are not certain that all stationary Scud launchers have been destroyed, but they continued to focus the hunt on the more elusive mobile launchers. "We are nowhere near completing our campaign objectives," said Air Force Maj. Gen. Burton Moore.

The Scud attacks were described more as an instrument of political terrorism than a serious military threat, given the minimal damage they have inflicted so far and the success of Patriot missiles in shooting down those launched. "They are absolutely not militarily significant," said Kelly. But the political importance of eliminating the Scuds has put added pressure on the allied forces in the gulf.

Military officials said they do not know how many mobile launchers remain, and a variety of numbers have been offered in private briefings in recent days. Cheney said the Iraqis have two types -- those supplied by the Soviets and "a home-grown variety" made by turning trucks into launchers.

British Defense Secretary Tom King told reporters that the allied forces had identified 10 more mobile launchers and that three may have been destroyed in recent bombing attacks. Kelly also said that Iraq's use of decoys had hampered efforts to locate the Scuds.

The Scud attacks on Israel have had a dramatic effect on U.S.-Israeli relations, which had been increasingly strained before the gulf war began. Symbolizing a new mood of enhanced trust and cooperation, Deputy Secretary of State Lawrence S. Eagleburger has been in Israel expressing gratitude for the Israeli government's decision not to retaliate so far for Iraqi attacks. "The entire atmosphere has completely changed," a senior Israeli official said. "They really are at pains to please us and be nice to us."

At the same time, Arab states in the international coalition arrayed against Iraq continued to offer assurances that possible Israeli retaliation for an Iraqi attack would not likely split the coalition. The defense and foreign ministers of Syria added their pledges of solidarity to those offered earlier by diplomats from Egypt and Sauda Arabia.POWs Appear Mistreated

Iraqi videotape of several allied prisoners of war, which was made available to American television and aired early yesterday, drew quick U.S. condemnation.

The pilots on the videotape, some of whom had cuts and bruises visible, spoke haltingly in criticizing the allied decision to wage war against Iraq. Their eyes appeared glazed, their bodies looked stiff and awkward and their voices had almost no inflection.

Navy Lt. Jeffrey N. Zaun showed signs of having been beaten, his face virtually covered with cuts and one eye swollen.

Another POW identified as a British pilot also appeared to have been severely beaten; his head slumped, his face was bruised and swollen and his words were almost unintelligible.

The pilots' appearances raised fears that they had been mistreated by the Iraqis. According to congressional sources, military officials report "almost conclusive proof" that at least some pilots have been tortured. British Defense Secretary King said the "remarkable uniformity of the statements, the voices in which they were delivered" created "suspicion of the means that may have been used to achieve those statements for their own political purpose."

Bush asserted that Iraqi treatment of POWs would not affect the operations of the allied forces. "This is not going to make a difference in the prosecution of the war against Saddam," he said. The State Department called in the Iraqi charge d'affaires to protest possible mistreatment.

Baghdad radio reported that the captured pilots would be dispersed among "civilian, economic, education and other targets," a statement indicating the POWs were being turned into "human shields," as Iraq did with civilians held for several months after the Aug. 2 invasion of Kuwait. Baghdad radio said the action was a response to what it claimed was allied shelling of civilian areas of Iraq, which it said had resulted in the "killing and injuring of Iraqis."

Cheney denied that allied aircraft had hit civilian targets in Iraq and said any use of the POWs as human shields would constitute "a war crime." British Prime Minister John Major called such use of captured fliers "inhuman, illegal and totally contrary to the Third Geneva Convention" and warned that those responsible could be prosecuted after hostilities ceased.

Some reporters questioned why Iraqi television, which first showed the pictures of the POWs, was still transmitting, given the heavy bombardment of the Iraqi capital. Pentagon spokesman Williams said that Gen. Colin L. Powell, chairman of the Joint Chiefs of Staff, had said the TV tower was "not a high priority target." Bush's Support Strong

The videotapes of the POWs brought the human side of the war into the homes of Americans, who until now have mostly seen a war of technological prowess by the allied forces. As the war wears on, there has been some slippage in public support, according to a new Washington Post-ABC News Poll, but Americans continued to back Bush's handling of the effort strongly. Two in three surveyed said the goal should be to topple Saddam, not just to liberate Kuwait. At the same time, about four in 10 said they favored the start of U.S. talks with the Iraqi government to end the gulf crisis.

Bush, suffering from what White House spokesman Marlin Fitzwater described as a cold, returned to the White House about midday from Camp David. Aides said he followed essentially the same routine he has since launching the military action last week, meeting informally several times with national security adviser Brent Scowcroft and talking by phone with other top advisers and with a string of world leaders.

Bush also signed an executive order exempting American military personnel from having to pay taxes on some of their income while in the gulf and from having to file tax returns by the April 15 deadline. Williams said enlisted personnel will pay no taxes on their military income, while officers will receive a $500-per-month tax exemption on their military income.

Fitzwater said Bush discussed the war with Turkish President Turgut Ozal, Spanish Prime Minister Felipe Gonzalez and Italian Prime Minister Giulio Andreotti. On Sunday, the president held lengthy conversations with the leaders of Saudi Arabia, Britain and Egypt.

Despite reports from Cairo that Egypt may be attempting to broker a cease-fire in return for a firm commitment by Saddam to pull his troops out of Kuwait, administration officials said yesterday that Bush and Egyptian President Hosni Mubarak have not discussed such an effort and that the United States is involved in no such discussions.

"No one here is familiar with any such effort," said a senior administration official about reports of efforts by Egypt, Iran, India, Yugoslavia and others to gain a brief cease-fire as a prelude to a possible Iraqi withdrawal from Kuwait.

"Our position since the day the war began was that the end to the war is in Saddam's hands. When there is a complete withdrawal, when they stop fighting and move out, then the war will be over," said a senior U.S. official.

In Cairo, a confidant to Mubarak said Egypt, in diplomatic conversations with other Arab nations, was considering seeking a cease-fire, news agencies reported. A report in Al-Ahram, a government-owned newspaper, said Egypt may propose a temporary cease-fire to allow Iraq to withdraw. Egypt's official Middle East News Agency quoted Osama el-Baz, Mubarak's top political adviser, as saying a meeting on the gulf would be held soon between the foreign ministers of Egypt, Syria and Saudi Arabia, but declined to say if the session would be used to propose an initiative to end the war.

But a spokesman for the Egyptian government denied Mubarak was seeking a cease-fire, and administration officials referred reporters to that denial.

Meanwhile, the Philippine government ordered the expulsion of a senior Iraqi diplomat, asserting it had "strong evidence" linking him to an attempted bombing Saturday near a U.S. government library in Manila. The expulsion of Iraqi Consul General Muwafak Ani was one of a series of steps taken by allied and neutral governments to counter Saddam's threats to use international terrorism as an arm of his war strategy.

In recent days, Austrian, Canadian and Egyptian authorities have announced the arrest of suspected terrorists, several of them Iraqis or others with ties to Iraq. The British said they have detained 72 Iraqis whom they consider security risks. Across Europe, governments were ordering Iraqi diplomats home or preparing such orders saying that large diplomatic delegations were unnecessary in time of war.

Military officials offered limited assessments yesterday of the damage inflicted by 8,100 air sorties since the outbreak of the war. Despite the immediacy of television news reports, most of the war remains invisible to the world, as allied bombers carry out attacks on targets throughout Iraq.

Congressional sources briefed by the Pentagon said the air attacks have weakened but not destroyed Iraq's command and control system and that the Iraqis still have the ability to detect U.S. aircraft as well as fire some of their surface-to-air missiles.

Lt. Gen. Kelly said U.S. force levels in the gulf have risen to more than 472,000, meaning nearly 50,000 troops have arrived since the war began.

Cheney, while speaking of the general success of the war to date, said allied forces would not rush to engage Iraq's heavily entrenched ground forces, part of a plan to minimize casualties. "We're prepared to run the air campaign just as long as we have to, to make certain that we've done everything we can to set the stage for a successful ground campaign at the lowest possible cost," he said.

Peter Arnett of Cable News Network, the only known Western journalist still in Baghdad, yesterday described a city virtually deserted by civilians, with those still there keeping in hiding. Arnett, whose reports are being censored by the Iraqi government, said he was not allowed to describe bomb damage or strategic targets and was limited to describing what he could see out his hotel window.

"Most of the population have either left town for the safety of the countryside or they're staying inside," he said. He described civilians "venturing outside to the banks of the Tigris river for water" and said most of the shops seemed to be closed, with the exception of a handful open for food being issued by the government. Propaganda in Iraqi Media

Arnett also said Iraqis are continuing to receive heavy doses of government propaganda in newspapers being printed daily and in state-run television reports. Newspaper reports, he said, showed chunks of debris described as downed U.S. and allied missiles.

A military analysis in one state-run newspaper, Arnett reported, claimed Iraq had proven it could absorb an attack in the first phase of the war and that in the second phase, the "grand war," Iraq would have the advantage of the fierce commitment of its ground forces.

The failure of Iraq's Scud missiles to hit any militarily significant targets in Israel or Saudi Arabia has not been revealed in the Iraqi media, Arnett said. Instead, Iraqi papers have reported extensively on the two waves of attacks on Israel, speaking "very proudly" of those attacks, he said.

Other journalists who have left the Iraqi capital for Jordan in the last 36 hours offered descriptions yesterday of the effect of allied bombing on Baghdad. The British Broadcasting Corp.'s Eammon Matthews said Baghdad's main telecommunications building was a terrifying sight, with only a metal frame left to the 15- to 20-story building. "All the floors have collapsed down to the first floor, like a pack of cards," he said.

Brent Sadler of Britain's Independent Television News said in a report from Amman, Jordan, that the destruction in Baghdad was "awesome and frightening." He said the attacks are having a "devastating effect" and he described a cruise missile slicing off the top of a building "like a surgical knife."

Sadler, like Arnett and Matthews, described a city where virtually all the civilians are out of sight, living underground in shelters, unable to return to bombed-out areas.

Defense Department officials disclosed that submarines had been deployed to the gulf and that "more than one" had fired cruise missiles against enemy targets. Members of the Navy's submarine service, normally reluctant to discuss their operations, were said by one official to be "ecstatic" about the results.

Pentagon officials would give only sketchy details of the firings, which were first disclosed by Rear Adm. Riley E. Mixson, commander of the Navy's Red Sea Battle Force, in an interview Saturday abaord the aircraft carrier USS John F. Kennedy. "Having let the cat out of the bag, I'd just as soon not skin it completely," Williams said, turning aside requests for more information.

Navy sources said the latest versions of the Los Angeles-class attack submarines are able to fire cruise missiles through vertical launch tubes, and earlier versions of the attack submarine can fire them from conventional torpedo tubes in the boat's bow and stern.

In his interview with reporters, Mixson also disclosed that bombers have successfully fired a new, high-tech missile called SLAM. The missile, officially known as the Standoff Land Attack Missile, was first announced by the Pentagon in summer of 1989 when it was undergoing its first tests.

The SLAM was described as "a derivative of the Harpoon missile system," designed for use on carrier-based aircraft. It carries an infrared camera that sends a signal to the pilot, who then aims the missile precisely at the target.

Contributing to this report were staff writers Al Kamen, Tom Kenworthy, George Lardner Jr., Bill McAllister and R. Jeffrey Smith, correspondents Jackson Diehl in Jerusalem and Jonathan C. Randal in Damascus, polling director Richard Morin and researcher Bruce Brown.