Apparently reneging on a ceasefire agreement with South Sudan’s government, former vice president Riek Machar said earlier this week he had formed a “resistance” movement to fight what he described as the “regime” of President Salva Kiir.

“We decided to organize a resistance against the regime,” Machar told Voice of America in a telephone interview, adding that he wants to see free elections and political pluralism take hold in Africa’s youngest country.

“So, yes, if you heard troops in Upper Nile, in Jonglei, in Unity States, in Equatoria saying what I am saying, yes, we are now an organized resistance against the regime,” he said.

The announcement could derail a truce that both parties agreed to late last month to end a conflict that the International Crisis Group believes has killed up to 10,000 South Sudanese since violence flared up most recently and displayed several hundreds of thousands civilians, according to the United Nations.

The provinces Machar mentioned are all in the north and east of the country and home to his Nuer people. His conflict with Kiir, who is a member of South Sudan’s largest ethnic group, the Dinka, has taken on a sectarian character and evoked memories of the massacre of some 1,000 Dinka at the hands of Nuer fighters in 1991. Machar, who led those Nuer fighters, apologized for the part he played in the atrocity when he was vice president.

Last year, Kiir reshuffled his cabinet dismissed Machar, accusing him of plotting a coup.

In his interview with Voice of America, Machar denied he had tried to oust the president whom he nevertheless accused of having “dictatorial tendencies.” He vowed to challenge Kiir for the leadership of the ruling Sudan People’s Liberation Movement ahead of the elections in 2015.