An ambitious U.S. logistics operation to feed famine victims deep in Sudan has turned into a disaster, with relief officials afraid that 500,000 to 1 million Sudanese may die of starvation.

The "sheer size" of Africa's largest country "defeats us all," the British director of an international relief organization said, warning of a "major tragedy" that could dwarf the Ethiopian famine.

Conceived 18 months ago with foresight and imagination and skillfully guided through the Washington bureaucracy, the project to deliver massive shipments of sorghum to Northern and Southern Darfur, Sudan's westernmost provinces, now lies in ruins, a textbook example of how not to run a relief operation.

Together with a similar operation in Northern and Southern Kordofan provinces, just to the east, where trucks are delivering sorghum again after a six-week interruption this spring, the U.S. relief program already has cost more than $400 million, including $100 million for transportation in Sudan.

At the heart of the Darfur failure lies what many observers criticize as overreliance on Sudan Railways. That notoriously inefficient, government-owned corporation, long impervious to outside pressure, was to have transported 1,300 tons of sorghum daily along the final 590-mile route from the White Nile city of Kosti west to Nyala in Darfur.

After successful initial deliveries in December and January, Sudan Railways abruptly ceased honoring its contract despite the doubling of normal freight rates for the grain shipments.

In retrospect, that doomed U.S. hopes of stockpiling sorghum in regional centers before the July and August rainy season made road distribution to villages all but impossible in the provinces, an area the size of France.

But U.S. Agency for International Development officials continued to hope that Sudan Railways would resume functioning normally and delayed turning to road transport as a major alternative.

In recent weeks starving villagers have been reduced to breaking open anthills in search of grain, tearing leaves off trees and eating mochet, the green berry of a poisonous bush that must be soaked for three days and then boiled before it is edible.

Hundreds of thousands of others have abandoned homes and fields to the encroaching desert, defeating the program's goal of keeping them on the land to prevent further ecological damage and potentially dangerous migrations to urban centers.

"We didn't think it was possible for Sudan Railways to fail entirely," an AID official said. "We thought they could manage at 30 percent efficiency."

In fact, Sudan Railways has managed to operate other services such as passenger and general freight trains, especially for enormous shipments of sugar for pastries and candy prized by the urban population during Ramadan, the just-ended Moslem month of daytime fasting and nighttime feasting.

U.S. officials said they remained at a loss to pinpoint reasons for the railway's refusal to deliver grain, despite repeated, well-publicized entreaties by Gen. Abdel Rahman Sawar-Dhahab, leader of the transitional military council that overthrew president Jaafar Nimeri in early April. But indifferent and incompetent management, possible union opposition to the weak military government, the decrepit condition of rolling stock and roadbeds, widespread corruption and a higher priority for traffic destined for urban centers than for remote villages are often cited.

"In the old days, we would have sent in the marines to run the railroads," a U.S. official said, "but we cannot do that anymore."

"I guess someone could make the point that we've made a complete flop of it," another U.S. official said glumly. "We'll have to take our lumps. We are going to come out as bad guys no matter what."

"We knew everything had to work out perfectly," the official added, "because no one had ever tried a relief effort as big as this one."

Summing up his frustration, Andrew Timpson, director in Sudan of Save the Children, which AID hired to distribute the grain to Darfur villages, said, "We've got the food in the country, first at Port Sudan on the Red Sea, then trucked to Kosti. We have the fuel to move it, and the relief workers were on the ground in Darfur before the food arrived. For the first time we felt we could prevent famine. We were going to have a buffer stock of 60,000 tons in place by June 1.

"And after six months, you'd think we'd done no work at all. You go out to Darfur and you'd think we'd only started. And the rains are coming."

Critics of the U.S. operation focus on the lack of management control and especially the absence of a backup delivery system by truck.

They pointed to the six-week break in March and April in truck deliveries of sorghum to Kordofan as evidence of AID's failings.

The hiatus in deliveries was caused when Sudanese truckers subcontracted by the U.S.-Sudanese firm Arkel Talab demanded higher rates for delivering grain to Kordofan after expiration of the contract covering the first shipments from Texas.

"They had the Americans by the throat," a foreign trucker from Port Sudan said. "They should have given part of the contract to outside firms to keep Arkel Talab and the Sudanese subcontractors from ratcheting up their prices for the subsequent contracts."

Even now, according to Emil Steinkrauss of CARE, the American organization under AID contract to distribute sorghum in Kordofan, lack of fuel has halved deliveries of grain rations for 1.3 million famine victims there.

"We're playing catch-up ball," Steinkrauss said, complaining that Arkel Talab had failed to deliver the fuel.

Had an extensive trucking network existed for the Darfur operation from the very beginning, critics argue, Sudan Railways would not have been able to choke off deliveries secure in the knowledge that no alternative transportation existed.

In any case, the critics said, some supplies would have reached the drought victims by truck in addition to the trickle of daily rail deliveries, which declined from 224 tons in the month before March 26 to 176 tons for the 75 days thereafter.

U.S. officials originally argued that bringing in big, desert-equipped trucks would collapse the Sudanese trucking industry.

During the past month AID belatedly has set up a trucking link from Khartoum across desert trails to El Fasher, more than 500 miles to the west in Southern Darfur Province. But so far, less than 2,500 tons of sorghum has been moved, and truckers have tripled their rates to the west in the past month.

U.S. officials are adamant that Sudan Railways not only can deliver the contracted amounts of grain, but, in fact, that it remains the only means of transporting the sorghum in meaningful quantities.

In the meantime, as more grain ships dock in Port Sudan, the sorghum is being funneled into warehouses, and U.S. officials worry that the stockpiles there may soon "get out of hand."

But despite some signs that the military government finally had prevailed on the Kosti railway workers to speed up grain shipments, deliveries in Nyala remain irregular and far below target.

In any event, truckers originally interested in moving the grain to 12 district centers have wandered off in search of steadier work.

And time is running out. On the basis of weather records, the Kosti-to-Nyala road can be expected to wash out four to six times during the two-month rainy season, each time requiring a week to repair.

Chris Eldridge, the Save the Children director in Nyala, said waiting for the grain trains to arrive had made him "numb with frustration and the thought of impending disaster."

Timpson, his superior in Khartoum, predicted an "explosion " of deaths next month and said that the area north of Geneina was likely to be the hardest hit.

Save the Children has chartered a 50-truck convoy to carry 500 tons of food to Nyala, but Timpson acknowledged that such an isolated effort could not solve the problem.

"It's symbolic," he said. "We just have to do something, no matter how desperate the situation is."

Since the end of May, the European Community, which originally had contributed almost nothing to the western Sudan relief operation, started an airlift with Belgian and West German air force transport planes.

Additional aircraft may be forthcoming from Britain, Denmark, France, Italy and the United States.

But the transport planes tend to tear up the rudimentary airfields in Darfur and, in any case, cannot move bulk grain effectively and are many times more expensive to operate than trains or trucks.

"With planes we're salving our conscience," one diplomat said, "not solving the problem."

Or, as a veteran disaster specialist remarked, "when you see C130s or any other transport plane flying supplies you know someone has goofed badly."

"It's going to be hard to explain why flying food is needed," an American relief worker said, "but it's going to be even harder explaining why people are going to die when food is piling up in Port Sudan and Kosti."