"Kofi, no food, hunger imminent," read a banner held up by a small group of children on the roadside as his convoy passed along the dirt streets of Rumbek, the southern bastion of former rebel leader John Garang. The government and Garang's Sudan People's Liberation Movement (SPLM) signed a deal in January to end a 21-year-old conflict that has left the vast expanses of southern Sudan with virtually no infrastructure and a precarious existence for many.

Donors promised $4.5 billion to bolster the peace deal at a conference in Oslo in April, but aid workers say donors are failing to send food needed to avert the south's worst hunger crisis since a 1998 famine in which at least 60,000 people died.

"The Oslo donors conference made a lot of promises ... We were happy with the pledges but they are not helping us now as our people would deserve," Garang said after talks with the U.N. secretary-general in a simple house with a corrugated iron roof.

"There are people actually who have starved to death and the U.N. food pipeline is virtually empty. So we are asking the secretary-general to please do something about it," he said as rain poured down on the town.

Annan responded, saying: "The U.N. team is here and we will redouble our efforts and we will press the international community to make good on their pledges. Cash today is better than cash tomorrow and we can help save lots of lives."

Annan was greeted at Rumbek's airstrip by hundreds of people. Some sang, while others climbed trees to see him. He was offered a traditional gift of white bulls to symbolise peace, which he said he would hand on to the needy.

HIGH MALNUTRITION

The southern conflict that erupted in 1983 claimed 2 million lives and spread across the south of the country, which has substantial oil reserves. But relief agencies worry that calls for help in the south may be drowned out by appeals for another conflict in Sudan's west.

Annan visited the western Darfur region on Saturday where a more than two-year-old conflict has left tens of thousands dead and 2 million homeless. He faced similar calls for help there.