Juba - South Sudan rebel leader Riek Machar has fired two high-ranking commanders, exposing widening rifts within the rebel movement and possibly weakening his negotiating hand at the latest peace talks.Machar's move is seen as a way of silencing two vocal generals who contributed to a recent rift between the political and military arms of the rebel movement.The rebels said Machar had sacked Major General James Gadet, the deputy military commander of the Sudan People's Liberation Movement-In Opposition (SPLM-IO) and Major General Gathoth Gatkuoth, the deputy chief of general staff for logistics.Gadet has been the subject of sanctions by the United States, European Union and most recently the United Nations, which accuses him of "fuelling the ongoing conflict and contributing to the devastating humanitarian crisis" in South Sudan.Thousands of people have been killed and more than 2.2 million displaced since South Sudan was plunged into war in December 2013, when fighting between rival factions of the army broke out in the capital, Juba.Power-sharing percentagesBoth sides have been accused of human rights abuses and indiscriminate killings which have often been carried out along ethnic lines, with Machar's Nuers pitted against the powerful Dinka community of President Salva Kiir.Gadet was replaced by Major General James Koang Chol, one of three rebel generals to come under the UN sanctions this month. Three government generals were also the subject of sanctions.Casie Copeland, an International Crisis Group analyst, said the re-shuffle was a move by Machar to sideline generals unhappy with his political leadership, but it would probably weaken his negotiating hand at peace talks in Ethiopia."The government sees Machar is having trouble keeping his house in order and may try to make deals with opposition commanders or ask Machar to demonstrate control over his forces before agreeing to power-sharing percentages in a deal," Copeland said."Machar has to be very careful how he handles this."Successive peace talks have failed, but officials say progress has been made at the latest round of discussions in Addis Ababa, with regional African leaders, Western powers and China all pushing for a power-sharing agreement.