US Secretary of State Condoleezza Rice, asked for her reaction to the expulsion order issued on Sunday, told reporters it was "unfortunate in the extreme."
"The situation in Darfur has been deteriorating and the international community needs very much to be able to act there," Rice said at a meeting with International Atomic Energy Agency director Mohamed ElBaradei.
She said she would try to discuss the issue with UN Secretary-General Kofi Annan. The United Nations said it still considered Pronk, who angered Sudan's government by saying morale was low in its army, to be Annan's special representative.
The United States was trying to get a "better handle" on the reasons for the expulsion, State Department spokesman Sean McCormack said. "We think that it's important that the UN has continued high-level access in Sudan," he said.
Rice wants to discuss with Annan ways to persuade Sudan to comply with a UN Security Council resolution to sent 22,000 UN peacekeeping troops to Darfur. Sudan has so far rejected the plan, McCormack said
During a visit to China last week, Rice sought to convince Chinese officials of the need to act on Darfur, McCormack said. China and fellow Security Council member Russia have been reluctant to impose sanctions on Sudan.
However, he said, "the sense we get is that the Chinese do understand the importance of getting an international force in there, and I think that they do have some influence with this regime."
He said Washington was also trying to enlist Arab states to press the case for an international force and allay Sudan's concerns. Sudan has said a UN force would amount to an invasion and attempted Western colonisation.

Copyright Reuters, 2006