DUBAI (Reuters) - A purported statement by Osama bin Laden (news - web sites)'s al Qaeda network denied it was behind last Sunday's deadly bombing in Saudi Arabia and warned it would carry out a new attack on a major U.S. city within two years. The statement, carried on Islamist Web site al-Mojahedun (holy fighters), also said that the militant group was behind all attacks against U.S. troops in Iraq (news - web sites). It was not possible to independently verify the authenticity of the statement, which used the Islamic calendar and had the language and style that is very...