Iran is claiming to have received advanced S-300 surface-to-air missiles capable of downing both aircraft and cruise missiles. This comes after Russia has still not delivered their S-300s due Iran in a 2007 deal. According to the Islamic Republic, they received at least two of these systems from Belarus, which that country denies.
The S-300 is capable of shooting down aircraft, cruise missiles and ballistic missile warheads at ranges of over 90 miles (144 kilometers) and at altitudes of about 90,000 feet (27,432 meters).
Iran is obviously announcing this in an attempt to scare off any potential attack on its nuclear sites. Of course, the American Air Force would be able to destroy these missiles with relative ease.