South Sudan's First Vice-President Riek Machar has rejected government claims that he and President Salva Kiir had struck a deal on the unification of their forces.

Cabinet Affairs Minister Martin Elia Lomuro on Sunday said the two had reached an agreement for a joint force which was critical for the implementation of the revitalised peace agreement.

Mr Machar's office in a statement termed the announcement as "false" adding that "the issue remains unresolved".

The minister had said the two leaders had agreed that the president's party takes 60% share of the unified forces with the remaining share being divided between Mr Machar's party and other opposition parties.

Mr Machar's office said previous talks had proposed an equal share between President's Kiir's party and his side while another proposal called for a 50:45 sharing.

President Kiir and Mr Machar formed a unity government in February last year and agreed, as part of a revitalised peace deal, to form a unified national army of 83,000 forces.