SUDAN'S military leader General Abdel Fattah al-Burhan has threatened to expel the United Nations' special representative, accusing him of overstepping his mandate. "We heard his slander the other day, lying, blatantly lying," Burhan said in a speech at a military graduation on Friday. "If you overstep your mandate, we will put you out of Sudan." The comments come days after U.N. representative Volker Perthes gave an update to the Security Council on efforts in Sudan, where he commented on the country's economic turmoil, violence against protesters and priorities for a transition to elections. Perthes' mission has involved holding a series…