Envoys from the top five UN powers, plus Germany, said that a "firm" international response was needed over Iran's nuclear program, but remained at odds over what measures to take after a Paris meeting ended without agreement.
With Iran striking a defiant tone, further negotiations were to take place in coming days as foreign ministers planned to gather in New York next Monday with the aim of producing a UN resolution acceptable to all.
The hardening stance against Iran, led by the West's push to impose sanctions, sent oil prices to a new record level on Tuesday. Brent North Sea crude for June delivery rose to US$74.97 a barrel.
The Paris talks were the first among senior representatives of Britain, China, France, Russia and the US, as well as Germany, since the International Atomic Energy Agency (IAEA) told the Security Council last Friday that Iran was in breach of a UN demand to halt uranium enrichment.
Nicholas Burns, the number three in the US State Department, said after the meeting with counterparts from the other countries that "all agreed that the Iran nuclear program should be suspended, and agreed to begin Security Council debate and start negotiating a resolution for suspension."
But he also voiced frustration with permanent Security Council members Russia and China which are opposing the US and its EU allies.
"It's time for countries to take responsibilities, especially those countries that have close relationships with Iran," he said.
Iranian Foreign Minister Manuchehr Mottaki ruled out any possibility of suspending uranium enrichment work as demanded by the UN Security Council and the country's top security adviser predicted Arab states in the region would reject US-led pressure.
The US, backed by Britain, France and Germany, fear Iran is on the path to building a nuclear arsenal under cover of developing atomic energy and wants to invoke Chapter 7 of the UN's Charter -- a passage that would open the way for sanctions and eventually even force as a way to freeze its activities.
But Moscow and Beijing, which are major trading partners with oil-rich Iran, are calling instead for a softer approach.
The US ambassador to the UN, John Bolton, said on Tuesday that if a tough resolution was stymied, his country was ready to form a coalition of allies to impose sanctions outside of a UN mandate.
"If we were faced with a veto by one of the permanent members, if for whatever reason the council couldn't fulfill its responsibilities, then I think it would be incumbent on us, and I'm sure we would press ahead to ask other countries or other groups of countries to impose those sanctions," Bolton told a congressional committee in Washington.
French foreign ministry spokesman Jean-Baptiste Mattei said the six countries involved in the Paris meeting agreed that Iran's nuclear program "is not compatible with the demands of the international community" and were concerned at its development.
He added: "It has been agreed to pursue discussions, in particular in New York, with the aim of reaching a firm decision from the UN Security Council and addressing a clear message to Iran."