The United States demanded an emergency meeting of the U.N. Security Council on Thursday over a letter in which Sudan s government said it would view any troop commitments to a future peacekeeping force in Darfur as a hostile act and a prelude to an invasion. Sudan has set itself on a path of confrontation with the international community, rejecting a recent U.N. Security Council resolution to deploy more than 20,000 U.N. troops to Darfur to replace 7,000 under-equipped African Union (AU) peacekeepers. Observers say Khartoum fears that U.N. troops may be used to arrest officials likely to be indicted by the International Criminal Court investigating alleged war crimes in Darfur.