The White House suggested Tuesday that President Bush might refuse to meet with Nigerian President Olesegun Obasanjo this week if answers are not forthcoming about the disappearance of indicted former Liberian President Charles Taylor.

Taylor has been indicted by a U.N. tribunal on charges of war crimes and crimes against humanity while in office.

He has been living in Nigeria under an agreement that helped end Liberia's civil war in 2003. Last week, Nigeria's government agreed reluctantly to surrender him to stand before a U.N. tribunal, but Nigerian officials said Tuesday that Taylor had vanished.

Bush is scheduled to meet with Obasanjo on Wednesday in the Oval Office. Asked Tuesday whether the meeting was still on, White House press secretary Scott McClellan said, "Right now, we're looking for answers from the Nigerian government about the whereabouts of Charles Taylor."

On Capitol Hill, Secretary of State Condoleezza Rice told senators it would be a matter of "utmost seriousness" if reports of Taylor's escape are true.

Sen. Patrick Leahy, D-Vt., said it would be inappropriate for Bush to receive Obasanjo under the circumstances. Rice, testifying before a Senate Appropriations Committee hearing, did not respond to Leahy's comment.

The charges against Taylor included aiding and directing a Sierra Leone rebel movement and trading guns and gems with the insurgents.

Taylor also has been accused of starting civil war in Liberia and of harboring Al Qaeda suicide bombers who attacked U.S. embassies in Kenya and Tanzania in 1998, killing 12 Americans and more than 200 Africans.

The United States, the United Nations and others have demanded that Taylor be handed over to the international war crimes tribunal in Sierra Leone.

Nigeria's government agreed last week to hand him over to Liberia, which almost certainly would have transferred him to Sierra Leone for trial.

McClellan directed questions about Taylor's whereabouts to Nigerian officials and refused to speculate about whether somebody within the Nigerian government was involved in Taylor's disappearance.

"It is the responsibility of the Nigerian government to see that he is conveyed to the special court in Sierra Leone," he said. "We expect the government of Nigeria to fulfill this commitment."

The State Department said there was deep concern about reports that Taylor had fled. Deputy spokesman Adam Ereli told reporters that U.S. officials are in contact with the government of Nigeria to determine Taylor's whereabouts.

Even though the Nigerian government has acknowledged Taylor's disappearance in a statement, Ereli said the United States was seeking final confirmation from Nigerian leaders.