BOR, SUDAN -- Amid the steamy swamplands at a bend in the White Nile River, a gleaming silver and white boat looms as a mirage. The Red Cross II is its name, a modern, $1 million river barge specially designed to cruise the treacherous marshes of Africa's longest river.

Its mission: to save lives by ferrying food and medical supplies -- through territory in the south held by rebels in Sudan's civil war -- to an estimated 500,000 civilians stricken by drought and epidemics hundreds of miles downstream.

But in Sudan, nothing is guaranteed.

More than four months after it arrived here, after being hauled 580 miles aboard six trucks from Kenya and painstakingly assembled by workmen, the Red Cross II remains idle.

As rust creeps along its waterline, and as the region plunges toward yet another famine, this potential Queen of the Nile is tied up by distant bureaucratic tussles and furious political opposition from Sudan's military rulers in the capital of Khartoum to the north. The barge, they insist, will be piloted by rebels to ferry not food or medicine, but tanks, missiles and guns.

In the mysterious and maddening world of humanitarian relief in Sudan, an eternally troubled East African country of 22 million people, precious few things are ever what they appear to be. What to some may seem a God-sent humanitarian tool to save the lives of thousands of innocents may be taken by others to be a frightful instrument of mayhem and death.

The saga of the Red Cross II typifies, in a wider sense, the hopes, failures and political complications of relief efforts throughout Sudan, where almost any commodity of earthly value -- from a bag of donated wheat to a powerful river barge -- is considered a prize worth fighting for by the rival armies.

In a civil war that has cost an estimated 500,000 civilian lives to famine and bloodshed since 1986, power often seems to grow not so much from the barrel of a gun as from gaining some form of control over the means and dispersal of international relief supplies intended for noncombatants. This is no small endeavor. Relief operations in Sudan currently cost about $400 million annually.

Right now, the Khartoum government is winning that struggle for control, but to the grave detriment, many critics charge, of millions of their own citizens in the south.

"Khartoum," said Egil Hagen, director of Norwegian People's Aid, a relief group with long experience delivering food and medicial supplies to the south, "is accomplishing more of its political and military ends by simply depriving the people of food than it could ever do with guns."

Nine weeks ago, this riverside town -- the site of a mutiny in 1983 by southern soldiers against Khartoum's Moslem government, an act that triggered Sudan's civil war -- was heavily bombed by two Soviet-made Antonov aircraft.

Many Western relief experts say the Red Cross II was a prime target of the raid by government planes. Instead, the bombs fell in the middle of rebel-held Bor, shattering huts, killing eight teenagers and wounding dozens of other civilians.

"It's just a terrible embarrassment," said a top official of the International Committee of the Red Cross, caretaker of the barge. The official insists that the relief organization is willing to do anything to get the boat moving but is stymied by Khartoum's opposition and the group's own mandate. He cited rules of strict impartiality in the Red Cross charter that require approval of relief operations by both sides in any conflict.

But despite the food emergency, the Red Cross has been forced to sharply cut back its operations throughout the country in recent months, on orders of Sudanese government officials, still livid over the presence of the barge.

"It's an utterly bizarre situation," said Roger Winter, head of the U.S. Committee for Refugees in Washington, a group that is lobbying the State Department to press Khartoum to leave the barge alone and let it do its work. "There is no humanitarian rationale for this kind of behavior."

While Khartoum demands that the barge be sailed to either the government-held towns of Juba or Malakal, or dismantled and taken out of the country altogether, rebels of the Sudan People's Liberation Army insist that it operate right where it is.

Commander Kuol Manyang Juuk, a top rebel military chief based in the rebel-held city of Torit, said he prefers that a foreign aid organization operate the barge, but that he cannot wait forever for the relief officials, Western donors and Khartoum to figure out what to do.

"I hope it does not come to this, but we may have to take it {the barge} ourselves," he said in an interview last week. "We can't let it go to waste while the people die."

Indeed, as a backdrop to the controversy, relief experts predict severe crop failures and yet another famine in Sudan in coming months in which an estimated 8 million Sudanese civilians may be affected. Many of the civilians are located in government-held areas but are expected to migrate to this region in search of aid. A few of these civilians who know about the barge seem bewildered by the whole thing.

"I know this boat is supposed to help the people," said Abbas Akon, an elderly Bor herdsman who sleeps in a tent near the Red Cross II and is entrusted by the town to keep constant watch over the barge. "But sometimes I don't understand the white man. He builds this boat and brings it all the way to Sudan. But then he does not use it."

In this searing vale of the White Nile, life is often defined by the horrors of war. Here, "Omar" is not just the first name of Sudan's leader, Gen. Omar Hassan Bashir, but also the fearful cry of terror the Nuer and Dinka people have come to scream whenever the government's Antonov bombers rain hell on their homes.

Once, this was a relatively vibrant region of rice plantations and oil drilling schemes. Now, it has been reduced to a valley of ruins, with old schools, hospitals and houses little more than rubble overgrown by weeds, a silent testament to an age just 20 years ago when electricity, road systems and running water flowed through parts of the area.

Two places, Bor and Ler, offer a study of striking contrast. While the Red Cross II shimmers in the sun at Bor, eight Western medical workers and their Sudanese counterparts labor in nearly complete isolation, in defiance of the government's order to stay away, at a makeshift hospital 200 miles downstream at Ler.

There, cut off from any regular means of supply, using an abandoned refrigerator door as an operating table, the doctors struggle to treat hundreds of Nuer and Dinka civilians suffering from war wounds and deadly diseases.

They say they are nearly out of food and medicine.

"We have enough for another few weeks," said Dr. Andre Griekspor, a 27-year-old Dutchman who digs foxholes for protection from bombs when he is not treating the ill.

Meanwhile, the war rages on.

On one side is the government of Gen. Bashir, who came to power 18 months ago in a military coup. He has cracked down on political dissent and has espoused fundamentalist Moslem doctrines while vowing to reinstitute a harsh form of Islamic law that mandates amputation for such offenses as theft.

His government, claiming that it is making great strides toward food self-sufficiency, has delayed acknowledging the nation's severe food shortages -- in fact, it insists that they are not as severe as Western relief experts have announced. Meanwhile, the government is spending scarce foreign exchange on weapons to fight the war, which is costing Sudan, already $10 billion in debt, about $1 million a day.

To further its war aims, the government has freely supplied arms to nongovernment Arab and tribal militias in the south. Human rights groups have accused these marauding bands of enslaving Dinka and Nuer civilians and committing widespread atrocities against them.

On the other side is the Sudan People's Liberation Army, which controls a large chunk of Sudan's predominantly Christian and animist south and is struggling to strike down the Islamic laws and gain an equal share of power in the northern, predominantly Arab seat of government.

Both sides are accused of wrongfully using foreign relief supplies. Critics charge that the SPLA feeds its troops with donated food at the expense of civilians, while the government is frequently accused of trying to starve and depopulate the south by withholding food and medical supplies intended for use here.

It was into this brew of political, religious, racial and ethnic strife that the Red Cross II came five months ago, an innocent gift of the government of Norway to the International Committee of the Red Cross. From nearly every vantage, the boat seemed a sensible idea.

The ICRC's plan was to base the vessel here in Bor, the northern-most site along the White Nile in Upper Nile Province that is reachable by overland relief trucks from the south before the terrain turns into the dense swamplands of the Sudd region.

The Sudd -- where befuddled European explorers repeatedly lost their way attempting to find the true source of the Nile -- is several hundred confusing miles of mud, muck, snakes, crocodiles and mosquitoes where the Nile breaks up into numerous twisting streams and stagnant pools thick with water lillies and dense vegetation.

The barge, powered by two diesel engines and specially designed propellers, was made to cruise through the Sudd and to make regular, two-day round-trip runs between Bor and the towns of Shambe and Adok downstream, key riverside sites that serve regions frequently affected by food shortages.

From Shambe and Adok, food and medical supplies could be transferred from the Red Cross II to trucks and sent overland to Yirol and Ler, from where road links easily could be established to remote Bahr el Ghazal province in the west.

Bahr el Ghazal, currently unserved by any established overland relief route, is perennially prone to drought and famines that have triggered catastrophic migrations of hundreds of thousands of civilians in recent years to Khartoum, southern Sudan and Ethiopia.

The plan seemed simple and reasonable.

Said one U.S. relief official in the region, "This is an infinitely preferable way to reach some very inaccessible areas west of the Nile. . . . It would be fantastic if we could get stuff in there."

And perhaps most importantly, the boat was sure to work cheaply. The Red Cross II is capable of carrying at least 60 metric tons of supplies at a cost of about $110 per ton, nearly $800 per ton less than the cost of the irregular airlifts used to serve parts of this remote region in the past.

At first, everything seemed to go well.

The barge was flown from London, where it was manufactured, to Nairobi and put aboard Red Cross trucks in July. But when it reached the Kenyan border town of Lokichokio, a reporter for Kenya's Nation newspaper found out about the barge and wrote an article.

Sudan's foreign minister, visiting Nairobi at the time, read the Aug. 1 article, which described the wondrous payload of the Red Cross II and its intended base of operations in the heart of rebel territory.

The bureaucratic battle began.

"We were a bit naive," said a Red Cross official, who, citing the "political sensitivity" of the issue, requested anonymity. He mentioned that the Red Cross I, a small boat used to ferry personnel along the river, was already in use in Bor at the time. "Since we were already working in Bor, we felt we could do this without Khartoum's explicit permission. . . . We were excited about what the barge could do."

So was Khartoum. The Bashir government, citing the barge's capacity to carry tanks, promptly restricted Red Cross operations to government-held zones. This was primarily because of the barge, but also because of an unrelated incident a few days earlier when rebel leader John Garang traveled to Addis Ababa, the Ethiopian capital, for a meeting with relief officials, reportedly aboard the private plane of a Swiss businessman.

Top officials of Sudan's government mistakenly believed the plane belonged to the Red Cross, and they angrily accused the relief group of transporting Garang, his men and weapons throughout the south.

This whole episode would seem almost madcap were it not for the fact that "the battle of the barge," as some are calling the dispute over the Red Cross II, has become a stumbling block for the conduct of relief operations throughout Sudan. "There is an element of mistrust that permeates the government's relationship with many relief organizations now," said the Red Cross official.

Most of these organizations operate under the umbrella of the United Nations' Operation Lifeline Sudan, a $340 million effort started two years ago in response to southern Sudan's 1988 famine, in which an estimated 250,000 people died. The U.N. operation was credited with saving many lives and helping to spur a nine-month cease-fire in the war that lasted until October 1989.

But now, many relief officials wonder if the U.N. operation is doing more harm than good for civilians in the rebel areas.

"The fact is, the U.N. can only work with a recognized member government," said Johan Hesselink, a Dutch relief official who works with a private organization in southern Sudan. "Operation Lifeline Sudan relies on the sanction and approval of Khartoum for its very existence. The problem is that Khartoum uses this power to influence operations and to block relief all over the south."

Hesselink recalled a time earlier this year when he asked a top official with Operation Lifeline Sudan for an emergency supply of syringes that were badly needed at the civilian hospital in Ler. Hesselink had managed to charter a plane with a bush pilot brave enough to defy Khartoum's ban.

But the U.N. official turned down Hesselink's request.

"He told me it just wouldn't look good if I was shot down and all these U.N. syringes were found in the wreckage of the plane," said Hesselink. "That's how political the business has become."

Critics, including Winter of the U.S. Committee for Refugees in Washington, say the Bashir government effectively holds veto power over U.N. operations in Sudan. They say that to continue their operations, many relief organizations and officials working with Operation Lifeline Sudan appear disinclined to defy or provoke Khartoum.

And, relief experts say, that is the chief reason the Red Cross II remains tied up. To get the barge moving, the Red Cross has offered to donate it to the U.N. World Food Program and Operation Lifeline Sudan -- but Khartoum has adamantly refused.

Many private relief officials say it is time someone stood up to the Khartoum government. Hagen, the Norwegian aid official, says it may be time to run the risk of operating the barge without Khartoum's permission, at night, if necessary, to avoid bombers.

"We want to respect the sovereignty of the state," said another top official of a leading international aid organization in Nairobi, "but in Sudan, you should begin to ask yourself, why must we always wait for the green light from this government?"