U.S., Iran held secret talks on march to nuclear deal --- (Reuters) - U.S. and Iranian officials met secretly in such out-of-the-way places as Oman, using military planes, side entrances and service elevators to conceal their efforts to lay the ground for Sunday's nuclear agreement. -- The contacts, first reported in detail by the Associated Press and later confirmed by U.S. officials and a former Iranian official, helped to bring about a deal that could help to end a decade-long impasse over Iran's suspect nuclear work. -- After four days of talks, Iran and six world powers - Britain, China, France, Germany, Russia and the United States, known as the P5+1 - clinched an interim deal curbing the Iranian nuclear programme in exchange for some sanctions relief. -- A former Iranian official confirmed the secret talks and said they took place with the wary approval of Iran's Supreme Leader, Ayatollah Ali Khamenei, who was sceptical of the outcome but agreed to all the meetings to take place. - More