U.S. President Barack Obama said Monday that he was “deeply grateful" for Ambassador Princeton Lyman as special envoy to Sudan and South Sudan upon his departure from his post. “Princeton has done a tremendous job in helping to realize the promise of an independent South Sudan, and working toward the international vision of Sudan and South Sudan living side by side in peace," Obama said in a statement. “I have valued his extraordinary service, which has been appreciated by the United States and the international community." “The people of Sudan and South Sudan, who have suffered so much, have the opportunity to seize a brighter future because of Princeton's efforts to urge both sides to put the interests of their people first. I am deeply grateful for Princeton's steadfast and tireless leadership, and wish him and his family well," Obama said.