The United States has urged Nigeria to ensure that former Liberia President Charles Taylor is sent to face trial on war crimes charges.
Charles Taylor stepped down in 2003 to end Liberia's civil war
Nigeria and Liberia have publicly disagreed over how Mr Taylor should be sent from exile in Nigeria to a UN-backed court in Sierra Leone.
Nigeria says Liberia should pick him up but now the US has backed up Liberia, which says it is up to Nigeria.
Mr Taylor faces 17 charges for allegedly backing Sierra Leone rebels.
He stepped down as Liberian leader in 2003 and went into exile in Nigeria as part of a deal to end the civil war he had begun 14 years earlier.
But there is uncertainty over whether he still remains in his luxury residency in the south-eastern city of Calabar.
The BBC's Mark Doyle in Freetown says there are powerful political forces at play over Mr Taylor's fate.
Nigeria's President Olusegun Obasanjo is due to meet US President George W Bush in Washington on Wednesday.
"It is incumbent upon the Nigerian government now to see that he [Mr Taylor] is conveyed to the international court," State Department spokesman Sean McCormack said.
"Obviously, we have talked to President Obasanjo about this."
But on Monday, Mr Obasanjo's spokeswoman said Nigeria's job was done and Liberia's President Ellen Johnson-Sirleaf had been told she "is free to come and take President Taylor into her custody".
But Mrs Johnson-Sirleaf said she wanted her predecessor to be sent directly to Sierra Leone, as he had not been indicted by a Liberian court.
Desmond de Silva, chief prosecutor of the war crimes court in Sierra Leone, has called for Mr Taylor's arrest in Nigeria, saying he was worried that the former Liberian leader may flee.
He also described Mr Taylor as one of the three most important wanted war crimes suspects in the world.
Joseph Ushigiale, spokesman for the Nigerian state where Mr Taylor is living, told the BBC's Focus on Africa programme that he was "under very good protective custody" and had taken part in the just-ended census in Nigeria.
1989: Launches rebellion
1991: RUF rebellion starts in Sierra Leone
1995: Peace deal signed
1997: Elected president
1999: Lurd starts rebellion to oust Taylor
June 2003: Arrest warrant issued
August 2003: Steps down, goes into exile in Nigeria
"We can assure you Mr Taylor will not just walk away."
A number of Mr Taylor's supporters have been detained in Liberia amid fears they may stage an armed uprising.
Tens of thousands of people died in the interlinked conflicts in Sierra Leone and Liberia.
Mr Taylor is accused of selling diamonds and buying weapons for Sierra Leone's Revolutionary United Front rebels, who were notorious for hacking off the hands and legs of civilians during a 10-year war.
He also started the Liberian civil war in 1989, before being elected president in 1997.