"Hungry people cannot eat pledges," Annan said in an opinion piece in The New York Times three days after he called on the world to help Sudan at a donors' conference in Oslo, Norway, on Monday.

"Through long and bitter experience we've learned that donor pledges often remain unfulfilled. In Cambodia, Rwanda, Liberia and elsewhere, a large percentage of promised funds failed to materialize, and many lives were lost as a result," he added, noting that of 880 million US dollars pledged for Cambodian war rehabilitation in 1992, only 460 million dollars had been delivered three years later.

"Clearly, we must do better in Sudan. I urge donors to convert their generous pledges into cash without delay," he said of the 4. 5 billion dollars pledged. "And I urge the public to hold them accountable for their promises. This time, let us keep our commitments, and not turn a blind eye to a whole generation of Sudanese who have earned this peace and desperately need it."