Updated

With his capital surrounded by rebels, Liberian President Charles Taylor (search) said he would step down and take exile in Nigeria but urged the United States to send peacekeepers to ensure an orderly transition.

Meanwhile, a team of U.S. military experts left a base in Spain early Monday for the war-ravaged African nation to assess whether to deploy troops as part of a regional force, as the United Nations, Europe and the Liberians have sought. President Bush heads to Africa Monday for visits to five nations -- including Nigeria (search).

Taylor, who has been indicted by a U.N.-backed war crimes court (search) in Sierra Leone, gave no timeframe Sunday for when he would quit power. Nor did not specify whether the deployment of a peacekeeping force was a condition for his departure.

He said only that the deployment was "necessary ... to prevent disruption."

The calls for a peaceful transition increased pressure on Bush to send U.S. troops to enforce a cease-fire.

Holed up in the capital Monrovia, Taylor was under intense international pressure to step down. Bush said Saturday he would "not take 'no' for an answer."

The Bush administration also showed little enthusiasm for Taylor's acceptance of Nigeria's asylum offer.

White House spokesman Jimmy Orr said: "What the president has said is Mr. Taylor needs to leave and leave soon. He needs to leave so peace can be restored."

Nigerian President Olusegun Obasanjo met Taylor at Monrovia's airport to offer him asylum.

"I thank my big brother for coming," Taylor said. "He has extended an invitation and we have accepted an invitation."

But, Taylor said, "it is not unreasonable to request that there be an orderly exit from power." He said U.S. participation in an international peacekeeping force planned for Liberia was "crucial in every way."

Both Taylor and Obasanjo would not say when the Liberian president would step down, but Obasanjo said "we believe that it will not take place in the near future."

Both warned that too hasty a departure could spark new fighting in the West African nation, where hundreds were killed in a failed rebel push into the capital last month.

"We believe the exit should not take place in confusion ... in a way that will lead to more bloodshed," Obasanjo said. "We believe the transition should be orderly and peaceful." He said the peacekeepers' deployment should take place "in a very, very short time."

Obasanjo, whose nation led a peacekeeping contingent that helped Liberia's 1989-96 civil war that led to Taylor's election the following year, said "international support" was required for a Liberian peacekeeping mission,

West African nations, he said, had the military "manpower" to stop the fighting but lacked the funds.

In the United States, Sen. John Warner, the Armed Services Committee chairman, said that Congress should hold a vote on any U.S. troop deployment to Liberia.

Because of the deadly chaos in Liberia, "we've got to think through very, very carefully the insertion of U.S. forces in there," Warner said.

Rebel officials said they had no confidence Taylor would follow through and leave Liberia.

"I hope this time around Mr. Taylor will act on his words," said a rebel leader, Kabineh Ja'neh in Accra, Ghana. "Far too often he has failed to honor what he says. We don't trust him. Not at all."

The visit by Obasanjo to bring the asylum offer in person underlined the urgency of international appeals for the Liberian leader to leave.

Taylor, who is facing a war crimes indictment issued June 4 by a Sierra Leone court, has said Liberia will not know peace until the charges against him are lifted.

Nigeria, like many countries, has no law allowing Taylor to be extradited to the Sierra Leone court for war crimes trial, U.N. officials say.

Taylor has been accused of supporting the brutal Revolutionary United Front rebels, whose trademark atrocity was amputating the arms and facial features of their civilian victims with machetes.

Bush is scheduled to land Tuesday in Senegal, one largely peaceful West African nation that hasn't seen the ill effects of years of war-making by Taylor -- a former warlord long accused of sowing strife in the region by aiding rebel groups.

Nearly one third of Liberia's 3 million people have been forced from their homes by fighting since rebels took up arms against Taylor in 1999.