Yesterday Iran claimed it had test-fired an advanced missile that could potentially reach Israel and U.S. bases in the Gulf. Secretary of State Hillary Clinton warned that a nuclear armed Iran would “spark an arms race in the Middle East." The missile test and the U.S. response comes in a week when politics takes center stage in Iran. The Iranian President, Mahmoud Ahmadinejad, faces re-election next month and campaigning for that election begins formally on Friday. For more we turn Jon Leyne, the BBC's correspondent in Tehran.