The United States, which has curbed relations with South Sudan over its political impasse, on Thursday welcomed a deal on reaching a long-awaited unity government. Rebel leader Riek Machar said he would form a unity government with his arch-rival, President Salva Kiir, seeking to end a devastating war that has engulfed the impoverished nation since its independence in 2011. "We welcome Dr. Machar's firm commitment to form an inclusive unity government by February 22," Tibor Nagy, the top US diplomat for Africa, wrote on Twitter. sct/jm