DHAHRAN, SAUDI ARABIA -- Amid the chaos and violence of the Persian Gulf War, a small group of Saudi and foreign volunteers is racing against time to save endangered birds, turtles and other wildlife from the ravages of one of the world's worst oil spills.

Working in a converted cafeteria in the port city of Jubail, the volunteers attempt to clean thick, gooey crude oil off cormorants, grebes and other birds collected from polluted beaches to the north. The volunteers -- about 20 specialists from such organizations as Britain's Royal Society for the Prevention of Cruelty to Animals and 100 or so local recruits -- also try to warm the birds and feed them. But they may be fighting a losing battle.

Thousands of birds are believed to have died already, environmentalists say, and the survival rate of those caught and cleaned historically has been poor.

The slick continues to move south along the Saudi coast and has hit Abu Ali Island, regarded by ecologists as a highly sensitive habitat. It threatens Jubail, site of the world's largest water desalination plant. The plant is being protected by a string of booms placed in the water to deflect the oil away from intake pipes.

The environmentalists' efforts are hampered by the war. Floating Iraqi mines threaten efforts to skim oil from the gulf's surface, and military authorities have blocked access to oil-soaked beaches near Kuwait. Also, the Saudi government has given priority to protecting industrial sites rather than ecologically sensitive areas, and the cleanup reportedly is short on cash.

"It's a very frustrating environment to work in because of the war and restricted access," said John Grainger, an ecological expert attached to Saudi Arabia's National Commission for Wildlife Conservation and Development.

Saudi and foreign officials say the bulk of the oil spilled into the gulf during the war came from a deliberate opening by Iraqi forces of Kuwait's main oil-loading terminal around Jan. 24. U.S. warplanes later stopped the flow by firing missiles at an inland pipeline manifold that fed the terminal.

There is confusion over how much oil spilled. Initially, Saudi authorities estimated the spill at 11 million barrels of crude, making it by far the largest ever recorded. On Feb. 8, Abdulbar Gain, president of the Saudi Meteorology and Environmental Protection Administration, put the figure at about 7 million barrels. On Wednesday, the same agency issued a revised estimate of between 500,000 and 3 million barrels.

In comparison, the amount of oil spilled into Alaska's Prince William Sound in the 1989 Exxon Valdez incident came to less than 255,000 barrels.

According to a senior diplomat in Riyadh, the Saudi government may be trying to minimize the extent and impact of the spill because, with the war draining its coffers, it is unable adequately to finance a cleanup.

Regardless of the spill's size, environmentalists say, it ranks as a major ecological disaster. Nearly a third of Saudi Arabia's 640-mile Persian Gulf coastline is now exposed to the oil, with 72 miles of beach severely affected, Grainger said. The oil sheen now stretches about 170 miles from its source and in places extends more than 12 miles offshore.

The bulk of the slick now lies between the coastal town of Safaniya and Abu Ali Island, although hundreds of dead birds are reported scattered on the beach at Khafji, a northern Saudi border town that has been the scene of fierce fighting.

While the bulk of the spill has resulted from what President Bush has called Iraq's willful "environmental terrorism," at least four other sources have been identified.

The National Commission for Wildlife Conservation and Development has reported that an undetermined amount of oil from a tank farm at Khafji is merging with the main slick, and that about 100 barrels a day is flowing into the gulf from a leaking wellhead in the Khafji oil field. Small slicks also have been spotted south of Mina al Bakr and near the Marjan oil field, off the northern Saudi coast, the commission said. "It is unknown whether military action or lack of maintenance is responsible for these slicks," a statement said.

The environmental impact of the spill is exacerbated by the shallowness of the gulf -- its average depth is 35 meters -- and the slow rate at which it is flushed by exchanging waters with the Indian Ocean. To make matters worse, the gulf was already the most oil-polluted major body of water in the world before the latest spill, and the Kuwaiti oil that has been pouring into it contains high concentrations of toxic compounds, environmentalists here say.

One overlooked aspect of the spill, Grainger said, is damage to rich sea-grass beds, which he called the "engines for the whole ecosystem" in the gulf.

At risk from the spill, he said, are Green and Hawksbill sea turtles that are already on the endangered species list, as well as a marine mammal called the dugong. Sometimes known as a sea cow, the dugong is related to Florida's manatee. Specialists estimate that only about 7,000 of the rare mammals live in the gulf.

The most visible victims of the spill, however, are the birds, especially four diving species: the common and Socotra cormorant and the black-necked and great-crested grebe.

Several million migratory birds winter in the gulf, while millions of others stop on their way from Africa to northern Europe in a migration that is to start later this month, Grainger said.

When birds come into contact with oil, they lose their buoyancy as well as their insulation from cold, he said.

Even lightly oiled birds often die because they react by preening, thus developing tar balls full of feathers and sand in their stomachs.

So far, however, Saudi protection efforts have been directed mainly toward desalination and other industrial plants, a priority that has chagrined some environmentalists.

"You can turn off an industrial plant," one said. "But you can't turn off an environmental process. You can't turn off a migration."