Sudan's Darfur (search) region, already engulfed in a conflict that has forced 1.8 million people to flee their homes, faces a new threat — a drought that has all but wiped out this year's harvest, the top U.S. aid official says.

Andrew Natsios, head of the U.S. Agency for International Development (search), said farmers who stayed on their land during the 21-month conflict are now beginning their major harvest, but they're expected to reap just 10 percent to 15 percent of the normal yield.

"They have enough production from this crop to last perhaps until March, but certainly not until the end of December" 2005, when the next harvest will be completed, he said.

The estimate by the International Committee of the Red Cross (search) "means an 85 percent crop loss," and will be subject to another assessment by the U.N. Food and Agriculture Organization, Natsios said.

But the dearth of rain is already having an impact because "the boreholes, the wells, are drying up from water much earlier," he said.

Natsios said the impending food shortage was one of many crises the international community faces in Sudan. Others include worsening security and riots in camps for displaced people, massive looting of livestock by government-backed Arab militias and a government shutdown of trade in animals and grain in rebel-controlled areas.

"It's a very dangerous security situation," Natsios told journalists recently, one that has curtailed access by humanitarian workers. As a result, U.N. goals for food distribution and immunizing youngsters in Darfur won't be met this month, he said.

When ordinary farmers start running out of food in March or April, "we're going to have to increase the food allocation, so we need even more access, and we're going to have less if this continues," Natsios warned.

Darfur's violence began in February 2003, after two newly emerged rebel groups, the Sudan Liberation Army (search) and the allied Justice and Equality Movement (search), rose up against the Arab-dominated government in a fight for more power and resources.

The Sudanese government responded by unleashing Arab tribal militias against the region's non-Arab African farmers. The Janjaweed (search), as the militias are known, are accused of targeting civilians in a campaign of murder, rape and arson.

Natsios said in a statement that he was "greatly disturbed" by the latest violence — a reported attack Monday on the strategic North Darfur town of Tawilla which, if true, would violate a security agreement signed by the government and opposition parties in the Nigerian capital, Abuja.

A tribal dispute over livestock sparked the clashes that began Sunday and resulted in rebel SLA forces attacking the Janjaweed, a U.N. official said. During the clashes, 45 aid workers fled into the bush to hide and were later airlifted to safety by African Union helicopters.

Natsios, who has been visiting Sudan for many years and was in Darfur in September, said the Janjaweed "have looted perhaps as many as 3 million, maybe over 4 million, sheep, goats, camels, from the (African) farmers who have small herds."

The Janjaweed are selling and eating some of the stolen animals, but the SLA has blocked them from moving their own herds and the rest of the stolen animals from pastures in southern Darfur to those in the north, he said.

"The SLA said if you looted our animals, you're not moving," Natsios said.

As a result, the animals controlled by the Janjaweed have eaten all the pasture in the south and if they are forced to stay there they could start dying or getting animal diseases, he said.

"If there is not restitution by the Janjaweed tribes to the African tribes, there is not going to be an end to this conflict," Natsios warned.

To cope with the crop losses and avert widespread hunger, Natsios said the international community must also pressure the Sudanese government to allow trucks to cross from government-controlled areas and neighboring Chad into SLA-held areas.

"The markets are collapsing in the SLA-held areas because of the government ban on cross-border trade," he said. "The people whose crops are failing need to be able to sell their animals to buy grain. That's the coping mechanism in any famine."

The market closure is "a very dangerous situation" that must be stopped immediately, Natsios said.