Ambassador John Blaney met with rebels along with commanders of a West African peacekeeping force and a U.S. Marine expeditionary force, now positioned off Monrovia.
Rebels agreed to withdraw from the port and surrounding areas, pulling back completely from Monrovia by noon Thursday and surrendering control to peacekeepers.
Terms of the accord, a copy of which was obtained by The Associated Press, obligates the West African peacekeepers to deploy first throughout Monrovia.
The West African force, still less than 1,000 strong, has ventured only occasionally out of its airport base as it builds to its promised 3,250-member strength.
The rebels' promise came only a day after Charles Taylor handed power to a deputy and left the country for exile in Nigeria.
Taylor, a Liberian-born, Boston-educated business student who trained in guerrilla fighting in Libya, faces a U.N.-backed war-crimes indictment for his trafficking with a vicious rebel movement in neighboring Sierra Leone.
Standing U.N. sanctions against him and dozens of associates accuse him of diamond- and arms-trafficking with insurgents in much of West Africa.
Taylor's exit was unbowed.
"History will be kind to me. I have fulfilled my duties," he said, relaxed and smiling in a hymn- and prayer-filled ceremony that seemed part send-off, part revival, with the Liberian leader stopping once to compliment himself for being such a good speaker.
Hours later, Liberia's new leader pledged that his country has made a clean break.
"He is gone. He would not interfere with the day-to-day activities of the Liberian government," President Moses Blah told CNN Monday. "I am a truly independent president."
Taylor mentioned returning to Liberia despite admitted fears of assassination and the war crimes court's international arrest warrant. Nigerian security forces say privately they will monitor Taylor to keep him from continuing as Liberia's power-broker from exile.
In his interview, Blah also appealed to the U.S. Marines offshore: "Please come to Liberia and save us because we are dying. We are hungry."
Three U.S. warships briefly moved into view off Monrovia within minutes of Taylor's ceding power to Blah. But the Bush administration says there is no plan to send the thousands of troops onboard to the shore, as long as things remain peaceful, reports CBS News Correspondent Jennifer Donelan.
According to The New York Times, the three American warships were sailed closer to Monrovia merely as a show of force. "Now the people of Monrovia know we're there," a military officer told the newspaper.
In Denver, President Bush called Taylor's exile "an important step" but gave no hint whether it moved him closer toward deploying more U.S. troops to assist with peacekeeping or humanitarian relief efforts.
"It is an important step toward a better future for the Liberian people," Mr. Bush said.
The United States, which oversaw Liberia's founding by freed slaves in the 19th century, has provided some logistical support and funding to the West African peace mission. It has been under pressure to do more, but the White House has expressed worries about overstretching the military, already committed to big jobs in Afghanistan and Iraq.
Blah is to hand over power in October to a transition government meant to lead Liberia into elections, Kufuor said.