The Sudanese government ordered the chief UN envoy out of the country on Sunday after he wrote that Sudan's army had suffered major losses in fighting in Darfur and was mobilising Arab militias in violation of UN resolutions.
The order against the envoy, Jan Pronk, is likely to complicate international efforts to halt the killings, rapes and other atrocities allegedly committed by the militias in the strife-torn region of western Sudan.
"The presence of the United Nations is vital to hundreds of thousands of citizens of the Darfur region," said a European Union spokesman, Amadeu Altafaj Tardio, in Brussels.
In a statement distributed by the official Sudan News Agency, the country's Foreign Ministry accused Pronk of demonstrating "enmity to the Sudanese government and the armed forces" and of involvement in unspecified activities "that are incompatible with his mission."
He was given 72 hours starting at midday Sunday to leave, the news agency said.
In New York, UN spokesman Stephane Dujarric said Secretary-General Kofi Annan had received a letter from the Sudanese government asking that Pronk be removed from the post.
"The secretary-general is studying the letter and has in the meantime requested that Pronk come to New York for consultations," Dujarric said.
Pronk, a blunt-speaking former Dutch Cabinet minister, drew sharp criticism from the Sudanese armed forces after he wrote this month in his personal blog, www.janpronk.nl, that Sudan's military had suffered heavy losses in recent fighting with rebels in northern Darfur.
"Reports speak about hundreds of casualties in each of the two battles, many wounded soldiers and many taken as prisoner," he said.
Pronk also said the government was responding to the deteriorating situation "by directing more troops and equipment from elsewhere to the region and by mobilising Arab militia."
"This is a dangerous development. Security Council resolutions which forbid armed mobilisation are being violated," he added.
The Sudanese armed forces said Thursday that those remarks amounted to "psychological war against the Sudanese army" and declared that Pronk was "persona non-grata."
One day later the military demanded an official apology. Even before the blog appeared, Sudan's government had been at odds with Pronk over Western efforts to get Sudan to allow a UN force of 20,000 troops to take over peacekeeping in Darfur from a 7,000-member African Union force.
Violence has risen dramatically in recent weeks in Darfur, where more than 200,000 people have been killed and 2.5 million displaced in three years of fighting.
UN officials have said the African Union force is too small and ill-equipped to cope with the violence and protest civilians from rape, murder and pillage.
But President Omar al-Bashir has rejected a UN peacekeeping force, branding it as simply a bid to restore colonial rule.
Despite the move against Pronk, the official news agency said Khartoum was "committed to cooperate" with the UN and would work with a new envoy "in accordance with signed treaties with the UN and the current principles of international law."
In Geneva, Switzerland, UN spokeswoman Marie Heuze noted that Pronk's comments were on his private blog and reflect "only his personal views".
Britain condemned the decision and urged the Sudanese to reconsider.
"This step is counterproductive and will contribute nothing to solving the problems of Sudan," Lord Triesman, the Foreign Office minister for African issues, said in a statement.
Tardio, the EU spokesman, said the situation in Darfur is "deteriorating rapidly" and the United Nations has "a key role to play which goes well beyond security and the current discussions on the UN deployment".