UNITED NATIONS – U.N. agencies and other organizations allowed to remain in Darfur don't have the resources to fully replace the activities of 13 expelled aid groups who were helping millions in the conflict-wracked region, the U.N.'s humanitarian chief said.

The United Nations will try to fill life-threatening gaps left by Sudan's expulsion of more than half the aid workers from Darfur, John Holmes, the U.N. undersecretary-general for humanitarian affairs, said Monday.

But neither the world body nor the Sudanese government has the capacity to take over the work of 13 of the largest humanitarian organizations kicked out of the country, he said.

Those organizations were ordered to leave Darfur after the International Criminal Court ordered an arrest warrant for President Omar al-Bashir on charges of war crimes and crimes against humanity in Darfur. Sudan has accused them of cooperating with the Netherlands-based ICC.

The Netherlands-based ICC accuses al-Bashir of leading a counterinsurgency against Darfur rebels that involved rapes, killings and other atrocities against civilians. Up to 300,000 people have died and 2.7 million driven from their homes in the conflict since 2003, according to the U.N.

According to the latest U.N. figures, 7,610 people worked for the 13 aid groups 308 international staff members and 7,302 Sudanese, mainly from Darfur, he said. They represent more than 50 percent of the roughly 14,000 humanitarian workers from 85 organizations that had been working in Darfur, including about 1,000 international staff, he said.