U.S. President Barack Obama's top envoy to Sudan has urged Khartoum to resolve its differences with South Sudan, the world's newest country. U.S. Special Envoy for Sudan Princeton Lyman also called for an interim agreement by the end of July on the sharing of oil revenues if a final agreement is not reached, AllAfrica.com reported Friday. Testifying before the U.S. Senate Committee on Foreign Relations in Washington Thursday, Lyman said leaders in both countries have shown in the past year "their capacity to work together on the major task of separation and to overcome the great odds in their search for peaceful completion of the [2005] Comprehensive Peace Agreement." "The situation remains fraught with serious threats to peace," Lyman said. South Sudan became the 193rd member of the United Nations this week. "We look forward to the Republic of South Sudan joining us as a member of the United Nations and to working closely with its representatives," German Foreign Minister Guido Westerwelle said in a statement. Germany is leading the U.N. Security Council this month. The U.N. Security Council recommended South Sudan to the General Assembly Wednesday and accepted South Sudan as a member Thursday. South Sudan became a nation Saturday in a ceremony attended by world leaders, including U.N. Secretary-General Ban Ki-moon. Its capital is Juba.