"WFP is extremely concerned about a rapid rise in food prices in Sudan," she said. "Many more people than we had anticipated could be facing food shortages and the shortages of cereals could be worse than we thought."

The price of the staple, sorghum, has rocketed to $261 a tonne in early 2005 from $131 in early 2004, she said.

Meanwhile $22 million in donor funding received for existing WFP work in Sudan, where the agency feeds 5.5 million people in the east, south and west, had fallen far short of the $301 million sought for 2005.

The number of people at risk, mainly in Bahr el-Ghazal, Khordofan, Red Sea state and Kassala region, may be far more than the 5.5 million targeted for WFP supplies, she said.

She said many communities had planted less sorghum this year because they were tending to rely on a good 2004 harvest, preferring instead to grow cash crops like the soft drink ingredient gum arabic.

"We are talking about areas that are drought-prone, where malnutrition is huge. Any change in food prices has a very strong impact," she said.

A combination of drought, erratic rainfall and social upheaval because of war had aggravated the food shortages. WFP was trying to determine the extent of the problem.

UN emergency relief coordinator Jan Egeland said on Friday that the western Darfur region faced a new threat of famine if international efforts failed to stop fighting there.

After years of tribal conflict over Darfur's scarce resources, rebels took up arms against the government in February 2003, accusing Khartoum of neglect and giving preferential treatment to Arab tribes.