A West African leaders' summit opened amid political turmoil on Sunday after the military rulers of Niger, Mali and Burkina Faso cemented a breakaway union at a rival meeting.
The three countries announced they were forming a new confederation, and their defiant first gathering on the eve of the Economic Community of West African States (ECOWAS) summit marked another test for the regional bloc they split from earlier this year.
ECOWAS is already wrestling with sweeping jihadist violence, financial trouble and the challenges of mustering a regional force.
It was not clear how the fractured bloc would respond after Niger, Mali and Burkina Faso adopted a treaty establishing a "Confederation of Sahel States" in Niamey on Saturday.
But ECOWAS Commission chief Omar Alieu Touray said the three countries risked "political isolation" and losing millions of dollars in investments.
The break would also worsen insecurity and hamper the work of the long-proposed regional force, he said before the bloc began a closed-door session in Nigeria's capital Abuja.
"Our region is facing the risk of disintegration," he warned.
The juntas in Niger, Mali and Burkina Faso came to power in a series of coups over recent years and announced their joint departure from ECOWAS in January.
They have shifted away from former colonial ruler France and expelled French troops, with Niger's General Abdourahamane Tiani calling for the establishment of a "community far removed from the stranglehold of foreign powers".
"Our people have irrevocably turned their backs on ECOWAS," Tiani said on Saturday, rebuffing the bloc's pleas to come back into the fold.
The Sahel countries' ECOWAS exit was fuelled in part by their accusation that Paris was manipulating the bloc and not providing enough support for anti-jihadist efforts.
Several West African leaders have called for the resumption of dialogue and Sunday's summit was the first for Senegal's new President Bassirou Diomaye Faye, who said in May that reconciliation was possible.
Niger's ties with ECOWAS deteriorated following the July 2023 coup that brought Tiani to power, when the bloc imposed sanctions and threatened to intervene militarily to restore ousted president Mohamed Bazoum.
The sanctions were lifted in February but relations remain bitter.
Ahead of the ECOWAS summit, defence and finance ministers have been looking into funding a "regional force to combat terrorism and restore constitutional order," according to the ECOWAS Commission.
It has called for the establishment of an initial 1,500-strong unit, and one proposal was to then muster a brigade of 5,000 soldiers at a cost of around $2.6 billion a year.
ECOWAS has launched military interventions in the past, but its threat of doing so after the coup in Niger fizzled out.
As the bloc grapples with regional challenges, Touray warned it was facing a "dire financial situation."
There were also reports of a rift over the possible reappointment of Nigerian President Bola Ahmed Tinubu as ECOWAS chair.
Media adviser to the Nigerian president Bayo Onanuga told AFP that "while some countries want him to remain because the region has faced some crisis, the Francophone countries want the seat."
Several French-speaking countries sent their foreign ministers to Sunday's summit instead of their leaders.
Benin's foreign minister told AFP that President Patrice Talon would not be attending "for scheduling reasons" and denied a dispute, saying that Talon supported Tinubu's reappointment.
