Teams of American special forces have been authorised to conduct spying missions intended to pave the way for a military strike on Iran in case President Obama orders one, US government sources have confirmed. The military units would penetrate Iranian territory to reconnoitre potential nuclear targets and make contact with friendly dissident groups, according to a secret directive written by General David Petraeus. The document's existence was disclosed for the first time yesterday. It authorises an expansion in the use of US special forces throughout the Middle East, US officials said. However, it is the possibility of American troops operating...