NATO head Anders Fogh Rasmussen said Thursday he was very "encouraged" by Iran's pledge not to seek nuclear weapons, saying a more open approach was in Tehran's own best interest.

"I have been very encouraged by recent statements from the new Iranian leadership," Rasmussen said, stressing the need to resolve international concerns over Iran's contested nuclear programme.

"I think it is in Iran's own interest to engage with the international community," he said, adding that if that is what Tehran is seeking, then "I can only welcome it."

Earlier, Iranian President Hassan Rowhani told NBC News that "under no circumstances would we seek any weapons of mass destruction, including nuclear weapons, nor will we ever."

"We have never pursued or sought a nuclear bomb, and we are not going to do so," he said, according to the US network.

The United States, its Western allies and Israel fear that Iran's nuclear programme is ultimately intended to produce atomic weapons.

Iran insists the programme is entirely for peaceful purposes.