Niger's coup leaders have asked for help from the Russian mercenary group Wagner.
The request came during a visit by a coup leader to neighboring Mali.
Wagner is considering the request.
Niger's military government faces a Sunday deadline to release and reinstate the democratically elected President Mohamed Bazoum.
Defence chiefs from ECOWAS members finalized an intervention plan and urged militaries to prepare resources.
A mediation team sent to Niger on Thursday was not allowed to enter or meet with military government leader General Abdourahmane Tchiani.
