The US, Britain and France have expressed growing concern that Iran is pursuing a nuclear weapons programme and developing ballistic missiles capable of delivering nuclear weapons.
The three Western powers were joined by Russia and China, which have close ties to Iran, in calling on the government in Tehran to return to negotiations on its nuclear programme.
China's deputy UN ambassador Wang Ming said, without elaborating, that "at present new opportunities have emerged for restarting dialogue".
The five permanent members of the UN Security Council spoke after a briefing by the head of the committee monitoring sanctions against Iran. The council imposed a fourth round of sanctions against Iran in June for refusing to suspend uranium enrichment and start negotiations with the five permanent members and Germany.
The council briefing took place ahead of a meeting next week of foreign ministers from the six countries on the sidelines of the annual ministerial session of the UN General Assembly. Iranian President Mahmoud Ahmadinejad is among some 140 world leaders scheduled to attend the annual meeting and a summit to promote the achievement of UN anti-poverty goals that precedes it.
Ambassadors from the three Western countries highlighted a recent report by the International Atomic Energy Agency and comments made on Monday by its chief, Yukiya Amano, who said he cannot confirm that all of Iran's nuclear activities are peaceful, as Tehran claims, because the country has offered only selective cooperation to the UN nuclear watchdog and has rejected several inspectors.
US ambassador Susan Rice pointed to "clear evidence that Iran is refusing to take any step to begin resolving concerns that Iran is pursuing nuclear weapons - and continues actions that in fact deepen these concerns." Ms Rice also expressed concern that Iran is pursuing ballistic missiles capable of delivering nuclear weapons in violation of UN sanctions - a concern echoed by Britain's UN ambassador Mark Lyall Grant and France's UN ambassador Gerard Araud.
Tehran says its peaceful nuclear programme is aimed solely at producing nuclear energy, but Mr Araud said "Iran's nuclear programme has no credible civilian application."
The Western envoys said despite deep concerns about Iran's nuclear intentions, the offer of negotiations remains on the table. But Mr Lyall Grant also warned that they remain "determined to continue to respond robustly to Iran's refusal to comply with its international obligations".
The Western ambassadors urged the sanctions committee to quickly appoint a panel of experts to help monitor what countries are doing to implement the measures. The committee called on all countries to submit reports on actions they have taken, noting that only 36 countries did so within the 60-day requirement.