A team from the West African regional bloc ECOWAS left Niger without meeting the leader of the junta which seized power in a coup, a delegation member said.
The Economic Community of West African States delegation arrived in the capital Niamey on Thursday "but did not spend the night" as scheduled, nor meet with coup leader Abdourahamane Tiani or deposed President Mohamed Bazoum, the team member is quoted by Reuters news agency as saying.
The delegation was led by former Nigerian president Abdulsalami Abubakar and was initially due to meet Tiani to present ECOWAS's demands, according to the Nigerian presidency.
Regional powerhouse Nigeria holds the rotating presidency of ECOWAS, which imposed sanctions and on Sunday gave the putschists a week to restore Bazoum to power.
Nigerian President Bola Tinubu however said the bloc would do its best to resolve the crisis amicably but ECOWAS said it could resort to military intervention as a last resort.
Meanwhile, Niger's junta warned it would meet force with force.
"Any aggression or attempted aggression against the State of Niger will see an immediate and unannounced response from the Niger Defence and Security Forces on one of (the bloc's) members," one of the putschists said in a statement read on national television late Thursday.
The deposed President has said he was being held hostage by the soldiers that removed him from power and called for international help to restore constitutional order.
