KHARTOUM, Sudan — Sudan said yesterday that African Union peacekeepers would have to leave Darfur unless they accept a deal within a week that would effectively block a proposed U.N. force.

Sudan’s foreign minister, Ali Ahmed Kerti, said the A.U. troops, whose formal mandate expires September 30, could only stay on in the remote, war-torn western region if they accept Arab League and Sudanese funding.

Khartoum last week rejected a U.N. Security Council resolution for the deployment of some 20,000 U.N. troops and police in Darfur to replace the ill-equipped and underfunded 7,000-strong A.U. force.

Instead, it has launched a major attack reportedly involving thousands of troops and militias in the northern part of Darfur that rebels say are backed up by bomber aircraft.

The African Union has called for the United Nations to take control of the peacekeeping force, but Khartoum is steadfastly opposed to the presence of the U.N. troops.

The A.U. force has been unable to stop the humanitarian catastrophe in Darfur, where three years of conflict has killed more than 200,000 people and driven 2.5 million from their homes.

The conflict in Darfur began in 2003 when ethnic African tribes revolted against the Arab-led Khartoum government. The government is accused of unleashing Arab militiamen known as janjaweed who have been blamed for widespread atrocities.

The American government has described the rapes, killings, and other attacks as genocide.

The foreign minister gave the African body a week to respond to its offer or withdraw its troops from the country, a government statement said.

An E.U. spokesman, Amadeu Altafaj Tardio, warned of dire consequences if the A.U. is forced to pull out before a U.N. force can take over.

“There would be a very difficult scenario,” Altafaj Tardio said in a telephone interview. “We need a stronger force on the ground to ensure security. It is crucial to reach an agreement with the Sudanese before that deadline. There are 2.4 million internally displaced, those people will never come back to their villages unless they have security,” he said.

Sudan earlier had ordered the African Union troops out by the end of the month after the bloc insisted that it would hand over its mandate to the United Nations, but the ultimatum apparently marked a final attempt to keep the weak African force in Darfur.

Mr. Kerti said he issued the ultimatum at a meeting yesterday with the African Union representative in Khartoum, Nigerian Ambassador Baba Gana Kingibe.

“The foreign minister indicated to Kingibe that the Sudan has always advocated the presence of African force in Darfur and sought funds for the maintenance of that presence,” the statement said.

“The Arab League has offered support to cover the presence of the African Union forces after September 2006,” he said. A May peace deal signed by the government and one of the three ethnic African rebel groups operating in the region has had little effect in halting the violence.

U.N. officials and aid workers say the crisis has only deepened in recent months, with violence at a new high. The United Nations has warned of hundreds of thousands of deaths if aid operations collapse. Twelve aid workers have been killed in Darfur this year, most in the last two months.

President al-Bashir of Sudan has rejected the U.N. presence as an attempt to impose Western colonial control over his country, instead offering to send 10,000 government troops to Darfur.