But rights groups warn that aid efforts could fail without a quick end to violence in the western Sudanese region.

Aid agencies met behind closed doors with officials from leading donor countries on Thursday to speed up the flow of international help to the area, which the UN has called the world's biggest humanitarian challenge.

Hundreds of thousands of people have fled their homes, mostly to avoid government-backed militias accused by UN officials of carrying out ethnic cleansing.

The refugees' plight will become desperate with this month's onset of the rainy season, which makes roads impassable and hastens the spread of infectious disease.

Shattered truce 

The US government agency USAID has warned that over 300,000 people could die from sickness and hunger.

Arab militiamen are blamed for
atrocities against rebel villages

"This unquestionably is the most serious humanitarian crisis in the world today in terms of the number of people at risk and in terms of their condition," USAID administrator Andrew Natsios said ahead of the meeting.

The UN's Office for the Coordination of Humanitarian Affairs called early last month for some $140 million in urgent assistance for Darfur, where an 8 April truce between rebels and the government has been frequently broken.

UN officials said that appeal was still underfunded, although they gave no figures. They also declined to spell out how much the UN hoped to raise at Thursday's meeting. 
 
Unchecked militias

Although the Sudanese government is close to a final deal with rebels to end a long-running conflict in the south of Africa's largest state, violence has continued to rage in the west of the oil-producing nation.

Rebels accuse Khartoum of neglecting the impoverished area and arming Arab militias to loot and burn their villages.

Both sides have accused the other of breaking the ceasefire, which was intended to allow aid agencies access to the estimated one million people internally displaced in the Darfur region. At least another 120,000 have fled into neighbouring Chad.

British-based rights group Amnesty International, which recently undertook a fact-finding mission to the Chad refugee sites, said the international community must put more pressure on the Sudanese government to rein in the militias.