He was reacting to comments by the top U.N. envoy to Sudan who was reported as saying last week that Khartoum -- which has rejected the deployment of U.N. peacekeepers in Darfur -- might instead accept a prolonged and reinforced AU force.

"Sudan agrees that the African Union troops stay until the crisis is over, but not indefinitely," the official, who is an aide to Mohamed al-Dabi, the Sudanese president's top Darfur representative, told Reuters by telephone.

"No foreign force left any country without a timeframe set for its departure," the official, speaking on condition of anonymity, said.

He said a comment by U.N. envoy to Sudan Jan Pronk, reported in the local media, that the AU force's mandate be extended indefinitely, "complicates the matter."

U.N. officials were not immediately available for comment.

The Sudanese aide was speaking as top officials from the European Union and AU met in Addis Ababa to discuss ways of bolstering peacekeeping in Darfur, where a three-year conflict has killed roughly 200,000 people and displaced millions others.

Sudan has resisted international pressure to allow some 20,000 U.N. troops to replace a poorly funded, ill-equipped AU force of 7,000 in Darfur, in western Sudan.

President Omar Hassan al-Bashir has likened U.N. peacekeepers to an invasion force bent on regime change in Khartoum. Analysts say his government is also worried that some officials could be arrested on war crimes charges.

The mandate for African forces in Darfur expires at the end of the year.

Aid officials and diplomats, fearing a security vacuum in Darfur if African forces leave without an agreement to deploy U.N. troops instead, have begun discussing an option for an enhanced African role in Darfur that has been dubbed 'AU-Plus'.

That would involve an extended mission, augmented by U.N. support, with greater policing power for African troops.

"The AU-Plus is a Sudanese demand. We want the AU force supported by more troops and logistics from the international community," Dabi's aide said.

His comments followed remarks by the head of the EU delegation in Sudan, Kent Degerfelt, that Khartoum seemed open to strengthening the African role with increased logistical and financial support from the United Nations.

U.N. CONTRIBUTION?

European Commission aid chief Louis Michel said the AU needed increased U.N. support if it is to continue. The EU is the biggest financial contributor to the AU mission in Darfur.

"In the current situation, the African Union cannot assume completely the job if it does not have an important contribution from the U.N.," he told reporters.

In Finland, EU foreign policy chief Javier Solana said he understood that Bashir was close to accepting the AU-Plus presence in Darfur, citing such a step as progress toward a genuine U.N. force in the region.

AU commission chairman Alpha Oumar Konare vowed not to abandon Darfur but said the AU force needed more international support if it was to continue its mission.

"Under no circumstance can we leave Darfur without peacekeeping forces. But we know we must strengthen our forces," he said in Addis Ababa.

Violence in Darfur has increased since a peace deal was signed in May between the Sudanese government and one rebel group. The deal has fractured rebel groups and fueled tensions as all sides try to make territorial gains ahead of possible international intervention.

Weekend clashes among rebel groups forced international aid agencies, except for the International Red Cross, to flee the Greida refugee camp in southern Darfur, a Western aid worker told Reuters.

"The fighting was about a mile from Greida. It was heavy fighting ... with mortars and artillery," the aid worker said, speaking on condition of anonymity.

The Guardian newspaper reported that up to 40 people were killed when fighters loyal to the Justice and Equality Movement attacked men from a faction of the Sudan Liberation Army (SLA), which signed the peace deal.

But an AU spokesman in Khartoum, Noureddine Mezni, put the death toll at 11 people, including an elderly man, killed in factional fighting "that included elements from the Sudan Liberation Movement." The SLA is also known as the SLM.