Sudan on Sunday told Annan's special representative Jan Pronk to leave, accusing him of overstepping his mandate after he hit out at Khartoum over the Darfur crisis.
"It is unfortunate in the extreme," Rice told reporters, swelling a tide of international condemnation, as she met Mohamed ElBaradei, who heads the UN's nuclear watchdog body.
"The situation in Darfur is deteriorating and the international community needs to be able to act there," Rice said.
"I am going to speak to Kofi Annan later today."
The outspoken envoy acknowledged he had been asked to leave. He said he would fly to New York on Monday "for consultations" with Annan, two days ahead of the three-day deadline for his expulsion.
Pronk said he met State Minister for Foreign Affairs Ali Karti on Sunday, and was given a letter addressed to Annan informing him that the government considers the envoy's mission in Sudan "terminated".
The 66-year-old Dutch official angered President Omar al-Beshir's regime by criticising its handling of the crisis in Darfur and pushing for deployment of UN peacekeepers.
The European Union earlier voiced deep concern at Khartoum's decision and stressed "the United Nations plays a key role which must be reinforced".
"The United Nations is not only about a security element being discussed -- the eventual peacekeeping force -- but it allows hundreds of thousands of Sudanese to stay alive," said Amadeu Altafaj, spokesman for EU Development Commissioner Louis Michel.
British Foreign Office Minister Lord David Triesman also condemned the decision to expel Pronk as "counter-productive."
In an October 14 entry on his Internet blog, Pronk criticised the performance of Sudan's army against Darfur rebels, claimed morale among troops was low and linked the military to the infamous Janjaweed militia.
The military responded by accusing Pronk of "waging psychological warfare on the armed forces."

Copyright AFP (Agence France-Presse), 2006