US Under Secretary of State for Political Affairs R Nicholas Burns participated in informal talks with the other five countries, which led to the decision.

Talking to reporters on Tuesday, White House press secretary Scott McClellan said the London [Images] discussions allowed the parties to exchange views over Iran's decision to resume uranium enrichment and reprocessing activities, which eventually could allow the government in Tehran to produce nuclear weapons.

"What all parties agreed was that the regime's actions raise serious issues and it should return to the suspension of all enrichment and reprocessing activity," he said.

McClellan echoed British Foreign Secretary Jack Straw's comments on Monday that the issue is one of confidence and "...the behaviour of the regime in Iran... has a long history of concealing its activities from the international community, and therefore must show the international community that it is not developing nuclear weapons under the guise of a civilian programme."

At the United Nations, US Ambassador John Bolton said, "The issue of Iran's nuclear weapons programme is a classic threat to international peace and security, which is why the United States has felt for some time that the matter belongs on the Security Council's agenda."

Bolton, who is the chief US envoy to the United Nations, said involving the Security Council will not displace the IAEA, but will "strengthen the hand" of the agency in dealing with Iran.

Asked if the Bush administration was considering placing oil sanctions or an oil embargo on Iran, McClellan said the United States was "not going to prejudge what may take place at the United Nations Security Council," if the council addresseds the matter.

"The first step is to go forward with this board meeting of the International Atomic Energy Agency," he said, adding that the current focus is on the continuing discussions with the Europeans and others in the run-up to the meeting.

Complete Coverage: The Iran vote and after