U.N. Secretary-General Ban Ki-moon is worried about Iran's nuclear program but hopes a stand-off with the international community can be resolved through dialogue, he said in comments published in Italy on Friday.

The West believes Iran is seeking to build an atomic bomb while Iran says its nuclear program is for peaceful purposes. Last week it appointed a new negotiator widely seen as taking a tough line in international talks intended to head off an intensification of existing U.N. sanctions against Iran.

Asked whether he was concerned about Iran's nuclear program, he told the newspaper La Stampa: "Yes, I'm very worried about Iran's nuclear progress.

"I hope that, even with the change in negotiators, things can move forward; it is important to continue negotiating with Iran."

Ban said he had met Iranian President Mahmoud Ahmadinejad briefly during the recent U.N. General Assembly, and was prepared to meet him privately if necessary.

"I have said with great urgency on many occasions that the differences can be resolved through peace, through dialogue; a war or military action is not desirable in any way," Ban said.

The United States on Thursday imposed new sanctions on Iran, partly over its nuclear program, and has refused to rule out military action.

Political directors from the five permanent members of the U.N. Security Council -- the United States, Russia, China, France and Britain -- and Germany are expected to meet in Europe next week to discuss imposing a third round of U.N. sanctions.

Ban