US President Barack Obama has welcomed the enthusiasm shard among the Iranians as they go to polls to elect their new president.

"We are excited to see what appears to be a robust debate taking place in Iran," Obama told reporters in the White House.

Polls opened in Iran on Friday at 8:00 a.m. (0330 GMT) and closed at 22:00 (1730 GMT). The result of the election is expected to be officially declared within 24 hours.

"Obviously after the speech that I made in Cairo, we tried to send a clear message that we think there's the possibility of change, and, you know, ultimately the election is for the Iranians to decide," AFP quoted Obama as saying.

"Whoever ends up winning the election in Iran, the fact that there's been a robust debate hopefully will help advance our ability to engage them in new ways," Obama said.

War-era prime minister Mir-Hossein Mousavi (1981-1989), two-time parliament (Majlis) speaker Mehdi Karroubi (1989-1992 and 2000-2004) and Expediency Council Secretary Mohsen Rezaei made an effort against incumbent President Mahmoud Ahmadinejad, who has sought another term in office.

During their campaign Mousavi, Karroubi and Rezaei announced that they would adopt a different strategy in dealings with the West, promising to hold diplomatic dialogue with the United States.

Ahmadinejad, however, reiterated that he will not change his foreign policy should he be elected for anther term.