Mr Assad, meanwhile, has given the impression that an arms race is under way by saying that he expects Russia to deliver the S-300 air defence shield. This advanced missile system can destroy aircraft at a range of 93 miles, potentially giving Syria the ability to shoot down strike aircraft over Israeli territory. The S-300 would also make it riskier for America and its allies to impose a "no-fly" zone. Russia is believed to have signed a contract to supply the S-300, but Syria's armed forces would need about six months to make the system operational.