Iran's parliament on Sunday approved a bill requiring immigration officials to fingerprint US passport holders despite President Mahmoud Ahmadinejad's opposition to the measure, state-run radio reported. Under the bill, the government would inspect and fingerprint all US nationals upon arrival to Iran. The measure still needs approval from the country's constitutional watchdog, the Guardian Council, before it can become law. Ahmadinejad last month said he was against the bill because his administration had no opposition to ordinary Americans. The bill was drafted by conservatives seeking retaliation for the US requirement that Iranian visitors be fingerprinted.