"The UN is presently exercising pressures on the armed movements to consent to the AU team's assignment of locating the position," he said.

The UN envoy stressed that cooperation with the AU mission was an obligation on both sides under UN Security Council resolutions.

"The location of positions and separation of the feuding forces are provided for in all agreements of the joint ceasefire observation commission and in the UN Security Council Resolution 1591," he said.

The Sudanese government, which has been at the receiving end of repeated criticism from the United Nations and its agencies, seized on the rare rebuke for the rebels.

The Sudan Liberation Army and Justice and Equality Movement had "refused to cooperate with the AU verification team," junior foreign minister Al-Tigani Salih Fidhail said.

Khartoum "awaits a statement by the AU on the matter and, at the same time, awaits the international community and the European Union to declare their positions with regards to the attitude of the rebels towards the verification team," he said, stressing his government's "full cooperation".

Late last year it had been the government which had refused to declare its redeployment to the positions established under a 2004 ceasefire, prompting the breakdown of AU-sponsored peace talks in Abuja.

UN Secretary General Kofi Annan is to visit Darfur later this week after attending a donors' conference for the war-wracked western region in Addis Ababa Thursday, Pronk said.

On Friday, Annan will hold Khartoum talks with First Vice President Ali Osman Taha and Foreign Minister Mustafa Osman Ismail before heading to the South Darfur state capital of Nyala Saturday.

There he will visit the Kalma camp, one of dozens around the vast region where an estimated two-million-plus displaced people have made makeshift homes, as well as the nearby village of Lebedu village, which was reportedly destroyed by government-sponored Arab militiamen.

On Sunday, the focus of Annan's visit switches to south Sudan where a landmark January peace agreement between the government and the rebel Sudan People's Liberation Army promised an end to more than two decades of devastating civil war.

The UN chief is to visit the south's main city of Juba as well as the town of Rumbek, where the rebels have their provisional headquarters and where Annan will hold talks with SPLA leader John Garang, Pronk said.

He will then return to Khartoum later the same day for talks with President Omar al-Beshir and a closing press conference at the airport.