The United States urged Sudan's rulers on Saturday to curb Arab militia attacks in Darfur, saying peace efforts in the turbulent west should draw strength from an imminent end to a civil war in the south. U.S. Secretary of State Colin Powell, speaking on a visit to Kenya where he will witness the signing of a north-south peace on Sunday, said sanctions were still an option for the United Nations in its efforts to end Darfur's "terrible conflict". "We can't overlook that while we are celebrating tomorrow the achievement in North-South dialogue (we will be thinking about) the difficult, terrible conflict in Darfur." Powell was flanked by southern rebel leader John Garang and his main negotiating partner, Sudanese First Vice President Ali Osman Mohamed Taha, who will sign the comprehensive peace agreement in front of African heads of state. Powell said that in a meeting with Taha he stressed "the importance that we attach to the government of Sudan doing everything possible to rein in the Janjaweed and the militias and we also need to make sure that the (Darfur) rebels don't contribute to the problem."