A senior Russian official today said the delivery of S-300 air defence missiles to Iran has been delayed for unspecified technical reasons. <br/><br/>Interfax news agency quoting Alexander Fomin, Deputy Head of Russia's Federal Service for Military-Technical Cooperation, reports, the delay is due to technical problems. <br/><br/>Mr Fomin said, the systems will be delivered when these problems will be resolved. Fomin spoke with Interfax while attending a Defence exhibition in New Delhi.<br/><br/> The S-300 defence system is an advance mobile system that can travel at more than 2 km per second and can shoot down aircraft and cruise missiles from up to 150 km away. The United States and Israel were trying to persuade Russia not to sell the missile system to Iran because it could foil attempts to hit the country's nuclear facilities with an airstrike.