The United States and its European allies are trying to push the United Nations to impose the fourth sanctions against Iran in a bid to force Tehran to give up its nuclear program.

However, speaking of the ongoing six-power meeting, State Department spokesman Sean McCormack downplayed chances that the participants would reach an agreement on Iran due to their differences.

"I wouldn't set expectations high at all for this meeting actually producing a definitive answer on the substance and timing of a resolution," he said.

But he added that "We're looking for the most robust Security Council resolution we can get."

Foreign ministers of the six countries are expected to meet on the sidelines of the UN General Assembly session in New York later this month, the State Department said.

According to an IAEA report released on Monday, due to Tehran's block, the UN nuclear watchdog had been unable to make much progress in investigating Iran's suspect nuclear program.

The United States and its allies have accused Iran of developing nuclear weapons, but Iran insists that its nuclear program is only for peaceful purposes.

Iranian President Mahmoud Ahmadinejad shrugged off international sanctions threat on Thursday. "Whatever they do, Iran will continue its activities. Sanctions are not important," he told a news conference. "The era of such threats has ended."

Iran till now has been under three UN sanctions over its disputed nuclear program.