By Michael Georgy CAIRO (Reuters) - One of Egypt's wealthiest businessmen said he had not invested any of the $500 million (327 million pounds) he pledged to his country in March because of the slow pace of reforms promised by the government. Naguib Sawiris, who has made an eye-catching but as yet unanswered offer to buy an island from Greece or Italy to house refugees from wars in the Middle East, said he had invested "zero" in Egypt since an upbeat investment summit in March. The chairman and chief executive of Orascom Telecom, Media and Technology, blamed bureaucracy and middle-level officials in Egypt for what he called "stagnation".