"The president feels very strongly and very passionately about the need to get an agreement, about the need to get a robust security force, a blue-hatted (U.N.) force in to be able to protect the innocent people of Darfur," Rice said.
Zoellick's intervention came after tens of thousands of people held "Save Darfur" rallies across the United States on Sunday, calling for an end to atrocities in Darfur and for more U.S. involvement in resolving the crisis.
A Sunday deadline set by the African Union for Darfur rebel groups and Sudan's government to reach a deal was extended by 48 hours and the U.S. government hoped a major push would break the deadlock.
Rice said no one wanted to see the situation in Darfur continue and there also needed to be urgent military and logistical planning for a U.N. mission and for NATO help.
"Frankly we need to shake the trees a bit, shake the bureaucracy a little bit and say to people it's not acceptable to wait any longer for at least the planning for a robust security force," Rice told reporters.
So far, Khartoum has refused the offer of U.N. peacekeepers to supplement about 7,000 African Union troops struggling to keep the peace in Darfur, a region about the size of France.
Asked whether she thought Zoellick would manage to broker a deal in Abuja, Rice declined to make any predictions. But her spokesman called Zoellick "results-oriented."
"You have to pick your spots when it is the right time to engage on the ground personally. And Deputy Secretary Zoellick decided that this was the right moment to try to get this over the goal line," said spokesman Sean McCormack.
But chances of a breakthrough appeared slim when Sudanese Vice President Ali Osman Mohamed Taha left Abuja on Monday. A diplomat said Taha believed the rebel leaders did not want substantive talks.
McCormack urged Sudan's government to send a senior representative back to Abuja, adding that while some progress had been made, key issues still had to be resolved.
The rebels, who have major objections on issues related to security, power-sharing and wealth-sharing in the peace deal, took up arms in early 2003 in ethnically mixed Darfur over what they saw as neglect by the Arab-dominated central government.
Khartoum used militias to crush the rebellion, killing tens of thousands of people in the fighting. A campaign of arson, looting and rape has driven more than 2 million from their homes into refugee camps in Darfur and neighboring Chad.
In Abuja, Zoellick will also meet Nigerian President Olusegun Obasanjo as well as the commanders of the AU mission in Sudan to discuss deteriorating security in Darfur