Iranian President Mahmoud Ahmadinejad criticised "brother" Turkey over its plan to host an early-warning radar as part of NATO's missile defence system, the presidency website reported on Friday.

"Turkey is among our brothers and close friends but when the enemies install a missile shield there and acknowledge that this act is against Iran, then one has to be watchful," Ahmadinejad was reported as telling a group of visiting Kuwaiti journalists Thursday evening.

"All know that America cannot defeat Iran ... but Iran is concerned about its brothers in the region and when we say that we are against foreign intervention ... it is because they see no other way but to sow discord among friendly nations to advance their interests," he said.

Ahmadinejad said Iran seeks brotherly relations with all regional nations," but that "some may be found to act under their influence and plots as the enemies' loudspeaker," he added without elaboration.

On Friday, Turkish foreign ministry spokesman Selcuk Unal said in a weekly news conference in Ankara that, "this system is not against any country. It aims at the defence of the NATO sphere."

On Thursday, Tehran toughened its criticism of the Turkish plan to host the early warning radar system allocated by the United States to NATO, saying it would create tension and lead to "complicated consequences."

Leaders of the 28-member NATO alliance gave their backing last year for the Europe-wide ballistic missile shield -- which US officials say is aimed at thwarting missile threats from the Middle East, particularly Iran.

Iran has made maintaining a good relations with Ankara a priority in recent years, and has considered Turkey an ally for its refusal to implement Western sanctions against Tehran over its controversial nuclear programme.