The government of Sudan has ordered UN envoy Jan Pronk to leave the country within three days.
The order was reported by Sudan's official news agency and did not say why Pronk must leave the country.
But last week Sudan issued a protest to the UN envoy over comments he made about Sudanese army forces in Darfur.
Pronk wrote on his personal website that the Sudanese army had lost two major battles to rebels in Darfur and morale was low as a result. He also said some soldiers were refusing to fight.
A military spokesman denied Pronk's allegations on Friday, and said Pronk was interfering in army affairs.
Khartoum began a military offensive in August against Darfur rebels who refused to sign a peace agreement with the government.
More than three years of fighting in the region has killed an estimated 200,000 people and displaced more than two million others from their homes.
Khartoum continues to reject calls to allow a UN peacekeeping mission in the region.
Information for this report is provided by AP, AFP and Reuters.