The UN-backed war crimes tribunal in Sierra Leone has welcomed a new call for the prosecution of former Liberian President Charles Taylor.
Charles Taylor is still considered to be a destabilising influence in the region
The Guinea and Ivory Coast presidents have called for Mr Taylor to be tried for supporting rebels in Sierra Leone.
They said moves to end conflict in the region are threatened by his impunity for alleged war crimes.
Mr Taylor is currently living in exile in Nigeria after stepping down last year under a deal to end the civil war.
The BBC's Mark Doyle says the call for Mr Taylor's prosecution is, on the face of it, a call to end impunity.
But it also confirms a new alliance between Guinea and Ivory Coast which UN peacekeepers present in several countries in West Africa will now watch carefully.
On Wednesday the UN war crimes court in the region welcomed the call for the prosecution of Charles Taylor.
However, both Ivory Coast and Guinea backed anti-Taylor factions during the Liberian civil war and the enthusiasm of the Ivorian and Guinean leaders for due legal process has to be put in this context, our correspondent says.
Mr Taylor is accused of backing the Revolutionary United Front rebels who waged a 10-year war in Sierra Leone.
They were notorious for mutilating civilians by hacking of their hands and limbs with machetes.
He stood down as Liberian president last August when rebels, allegedly backed by Guinea, closed in on the capital, Monrovia.
Nigeria agreed to give him asylum and has said it will not hand him over to the UN-backed Special Court for Sierra Leone.
UN peacekeepers are deployed in Liberia and Sierra Leone and are due to go to Ivory Coast.
Armed men often crossed the region's porous borders to take part in all three conflicts.
The BBC's Mark Doyle says that the continuing and potentially destabilising presence of Mr Taylor in the region is a reminder that the area's problems are far from over.