Escalating violence in the Sudanese region of Darfur (search) is threatening aid for millions of people as increasing numbers of international staff come under attack, the U.N. humanitarian chief said Wednesday.

"My warning is the following: If it continues to escalate, if it continues to be so dangerous on humanitarian work, we may not be able to sustain our operation for 2.5 million people requiring lifesaving assistance," said Jan Egeland, head of the United Nations Office for the Coordination of Humanitarian Affairs.

"It could all end tomorrow. It's as serious as that," he told reportersment in Darfur by the end of 2005."

The crisis in Sudan's western region of Darfur erupted when rebels took up arms against what they saw as years of state neglect and discrimination against Sudanese of African origin. The government is accused of responding with a counterinsurgency campaign in which the ethnic Arab militia, known as Janjaweed (search), committed widespread abuses against ethnic Africans.

At least 180,000 people have died in the Darfur conflict — many from hunger and disease. The fighting has driven some 2 million people from their homes.

The U.N. is providing food and medicine to some 2.5 million people in Darfur but has no security force there to help protect civilians and ensure that aid can be safely delivered.

Egeland said more pressure needed on the two sides to stop the violence.

"As they meet in Abuja, most of their attention seems to be on attacking each other and attacking civilians in Darfur," Egeland said. "Civilians are being killed and raped everyday across Darfur with impunity."

The African Union (search) maintains a force in Darfur of 6,000 troops, who can intervene if they witness human rights violations. U.N. officials say violence has declined where the troops are stationed, though other areas remain insecure.