KHARTOUM (AFP) - Sudan will withdraw its troops from the Abyei area which it seized a year ago only after a joint administrative body is established, the foreign ministry said on Sunday.

The comment followed a call by UN leader Ban Ki-moon late Saturday for Sudan to move its troops out of the disputed territory, after rival South Sudan withdrew its police from the area.

Under a May 2 UN resolution that seeks to end weeks of border fighting and resolve protracted disputes between Sudan and South Sudan, both countries are to pull their forces out of Abyei by this Wednesday.

They had already agreed last June to withdraw.

"We are committed to implement what we signed in June last year to withdraw from Abyei," Khartoum's foreign ministry spokesman Al-Obeid Meruh told AFP.

But he said a joint administrative body for Abyei must be in place first.

Under the June pact, the Abyei Area Administration will be headed by one of three nominees from the Sudan People's Liberation Movement (SPLM) -- which last July became the new government in South Sudan when it split from the north under a peace deal that ended 22 years of civil war.

The Sudanese government must agree to one of the SPLM nominees, and the SPLM in turn must approve one of Sudan's three nominees for deputy administrator, the June pact said.

"South Sudan rejected our nominations. We accepted theirs," Meruh said.

Under the June deal Sudan and South Sudan were to deploy an equal number of unarmed observers. They would be backed up by Ethiopian peacekeepers from the United Nations, whose force in Abyei now numbers 3,700 troops.

Meruh said the monitoring mechanism is not yet in place.

"The UN must not be selective. It has to ask for full implementation of the protocol," he said.

UN spokesman Martin Nesirky said UN chief Ban "welcomes the withdrawal of the South Sudan Police Service from the Abyei area. He strongly urges the government of Sudan to also remove its forces from the area."

Nesirky announced on Friday that the South had withdrawn hundreds of police that were based in Abyei but he said the UN was still "verifying" the pullout.

Sudan still has several hundred troops in Abyei and South Sudan has a similar contingent close to its border with the territory.

Under the May 2 UN resolution, both countries were to also pull back troops from along their disputed frontier, but Khartoum said it could not comply until there is agreement on where the border lies.

South Sudan said it had pulled its troops back in line with the UN call.

Abyei was to hold a referendum in January 2011 on whether it belonged with the north or South but that ballot was stalled over disagreement on who could vote.