Sudanese obstacles could mean the UN mission in Darfur is not viable, the head of UN peacekeeping has said.
Jean-Marie Guehenno told the United Nations Security Council that excessive demands from Khartoum "would make it impossible for the mission to operate".
Among other demands, Sudan wants advance notice of troop movements and to be able to shut down communications.
Mr Guehenno said the UN would have to consider whether a deployment would be worthwhile under such conditions.
The 26,000-strong United Nations and African Union peacekeeping force, Unamid, is due to take over protecting the people of Darfur in a month's time.
But Sudan has raised a series of objections which Mr Guehenno said threaten the success of the mission.
Sudan has still not agreed to the presence of non-African personnel and has not yet given the UN the land it needs to operate nor authorised night flights.
Mr Guehenno said it would be impossible to operate in Darfur under such conditions.
"Should the anticipated discussions fail to clear the path to the deployment of an effective force, the international community will be confronted with hard choices," Mr Guehenno said.
"Do we move ahead with the deployment of a force that will not make a difference, that will not have the capability to defend itself, and that carries the risk of humiliation of the Security Council and the United Nations, and tragic failure for the people of Darfur?"
Mr Guehenno added that Sudan's demands "create serious uncertainty with regard to the government's commitment to the deployment of Unamid."
The Sudanese ambassador responded by saying that the issues were only 'administrative problems' which should not be exaggerated.
The Unamid mission is aiming to bring security to the Darfur region after more than four years of conflict.
But it has been plagued by problems blamed on a shortfall in resources and lack of cooperation from Western and African states. ( BBC )