ADDIS ABABA, Ethiopia - Sudanese officials have asked international peacekeepers to leave a town in Darfur, the U.N. and Sudanese officials said Sunday. The challenge to the fragile international mission could pose a serious challenge to peace in the troubled region, observers said.

The Sudanese government asked peacekeepers to clear out of the town of Muhajeria, said Josephine Guerrero, a spokeswoman for the U.N. mission known as UNAMID.

Sudan wants to launch an offensive against rebels from the Justice and Equality Movement, a rebel group known to have occasionally received Chadian support that has held the south Darfur town since mid-January, said Akuei Bona Malwal, Sudan's ambassador to the African Union.

Malwal said the Sudanese government was requesting -- not demanding -- that peacekeepers leave.

"We are not ordering them around, we are asking them," he said. "It's sort of like informing them, 'something will be happening here.'"

Sunday's request is the first of its kind that the Sudanese government has made, U.N. officials said. Sudan has regularly challenged the U.N.'s presence in the country.

Sudan's army attacked a convoy of U.N. peacekeepers in Darfur, critically injuring a driver, barely a week into their new mission in the region in January 2008.

Sudan acknowledged that its troops shot at the convoy, but blamed the peacekeepers in part saying they should have notified Khartoum of their movements.

Senior U.N. officials will meet with Sudanese officials in Khartoum to discuss the latest request, Guerrero said. She said the request did not specify when the Sudanese government wanted the peacekeepers to leave the town of around 30,000 people.

Guerrero said the peacekeeping force would like to remain in place.

"Our mandate is to provide protection to civilians and we would like to continue doing that," she told The Associated Press.

Suleiman Sandal, a rebel commander, told the AP that his forces were anticipating a government attack on the town and have warned peacekeepers about the possibility.

"We have warned the UNAMID," he said by satellite telephone from Darfur. "We told them it is up to them. We care about their safety."

Reed Brody, a Brussels-based lawyer with Human Rights Watch who attended an African Union summit in the Ethiopian capital, said if UNAMID complies with the government's request, it could undermine the peacekeeping mission.

"The critical test for any decision like this is if it exposes civilians to attack by the government," he said. "And if it is, it is an undermining to UNAMID's key mandate. UNAMID is not there to affect the military balance of power, or to take sides, or even to facilitate attacks. They are also not there to protect the rebels. Or protect the government."

Rebels took up arms in Sudan's western Darfur region in 2003, citing neglect and marginalization by the central government. So far, 300,000 people have died and 2.7 million have been displaced.

Sudanese forces frequently bomb rebel areas in Darfur, despite a U.N. Security Council ban on military flights over the western region.