Egeland, the overall humanitarian aid coordinator for the United Nations, said the risks faced by the world body’s 11,000 relief workers in Darfur could soon be too great.

“The level of violence has been escalating again sharply,” he told reporters.

Renewed fighting is undermining a ceasefire between government and rebel movements which was agreed in April 2004 and which had largely held despite sporadic attacks.

“If it continues to be so dangerous to do humanitarian work, we may not be able to sustain our operations for 2.5 million people,” Egeland said.

“It could end tomorrow. It’s as serious as that.”

“We want to stay as long as we can. As we speak we have had to suspend action in many areas. Tens of thousands of people will not get any assistance because it’s too dangerous and it could grow exponentially.”

Egeland said the international community should ponder past failures, notably during the break up of Yugoslavia in the 1990s, when Muslims were massacred by Serb forces in areas purportedly protected by the UN and aid workers’ operations were hampered by violence.

“Is it a repeat of the safe areas of Bosnia all over again? We keep people alive, we give them food, we give them medicine but we don’t protect them and our own staff,” he said.

“So something has to happen. We need to have the same kind of pressure on the parties as we had (in 2004), when world leaders really put their thumb on the government of Khartoum and the guerrilla groups. I don’t think they feel the same kind of pressure.”

Last year, the UN Security Council threatened sanctions against the Sudanese government unless it disarmed the Janjaweed, and also called on the rebels to stop fighting.

Egeland said he hoped that all sides in the conflict will ”behave responsibly and not be utterly irresponsible as they are today.”

Egeland called for a force with “three times the strength they have today.”

“There are now in excess of 5,000 troops, which is better than they were last year, but it’s still incredibly behind what it should be,” he said.

“I still cannot believe how a hundred world leaders can say the biggest priority on earth is to get a large AU force in place and then, years after the crisis started, we still have a very inadequate force in place.”