The United States is incapable of inflicting "serious damage" on Iran, Iranian President Mahmoud Ahmadinejad said Tuesday, as a US Navy carrier group steamed toward Iran in what Washington has signalled is a warning to the country. Speaking in an interview with Iranian state television, Ahmadinejad said Washington had not stepped up its campaign against Tehran, despite the showdown over Iran's nuclear program which saw the UN Security Council impose sanctions on the country last month. "US rhetoric against Iran has not increased," Ahmadinejad said. "In 2003, they openly threatened to attack Iran. Now they have indirectly made such threats." Iranian opinion-makers have recently criticized Ahmadinejad, accusing him of stirring opposition to Iran by taking a hard-line on the nuclear dispute and employing inflamatory rhetoric.