Time may be running out for exiled Liberian warlord Charles Taylor, former president of the strife-torn West African nation once promoted as a homeland for U.S. blacks.

Liberia has formally asked Nigeria, where Taylor has lived since 2003, to extradite him, news services reported on Friday.

Taylor is accused of war crimes both in Liberia's 14-year civil war, which left hundreds of thousands of people dead and the country in ruins, and in a separate civil war in neighbouring Sierra Leone.

Former Liberian president Charles Taylor is in exile in Nigeria.(AP file photo)

A tribunal in Sierra Leone wants to try him for selling diamonds and buying weapons for a rebel group that was notorious for hacking off civilians' arms and legs, the BBC reported.

Nigeria's president, Olusegun Obasanjo, has refused to send Taylor to Sierra Leone, saying he would only be extradited after a request from an elected Liberian leader, Reuters reported.

Now Obasanjo has acknowledged receiving such a request from Liberia's Ellen Johnson-Sirleaf, who took power in January as Africa's first elected woman president, but he does not seem to be in a hurry to act.

Liberian President Ellen Johnson-Sirleaf has formally asked for Taylor's extradition.(AP file photo)

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Obasanjo's office issued a statement saying he will consult with other African leaders on how to proceed "in keeping with his commitment to give consideration to any formal request from a democratically elected government of Liberia" for Taylor's return.

There is a dispute about whether Taylor is immune to prosecution in Liberia under a 2003 peace deal in which he stepped down as president and went into exile.

His return, even as a war-crimes defendant, could inflame passions in Liberia, where he still has followers and his ex-wife is an elected senator.