South Sudan rebel faction leader Thomas Cirillo has rebuffed the invitation to meet the Inter-governmental Authority on Development (Igad) Special Envoy Ismail Wais.
The regional bloc on March 1, sent a letter to Gen Cirillo requesting his presence at a meeting slated for Friday in Addis Ababa- Ethiopia.
Gen Cirillo is the leader of the National Salvation Front (NAS) faction, which refused to sign the September peace agreement that re-united President Salva Kiir and his former deputy Riek Machar.
NAS spokesman Suba Samuel said the Igad invitation was exclusively to Gen Cirillo, and not his faction.
"It not possible to attend the meeting on the 8th because that letter is addressed to the leader of the National Salvation Front alone," Mr Suba was quoted saying by the Eye Radio in Juba.
The regional bloc recently threatened to designate Gen Cirillo as a 'peace spoiler' over his resistance to accept mediation.
Igad further ruled out any renegotiation of the September peace deal.
President Kiir has since agreed to offer Gen Cirillo a position in the upcoming unity government, if he joined the revitalised peace deal implementation.