"The Security Council has no option but to proceed with the Chapter 7," US State Department number three Nicholas Burns said, referring to an article in the UN charter that could lead to sanctions or even military action.

The talks in Paris were to take place late Tuesday involving top political directors of the five permanent UN Security Council members -- Britain, China, France, Russia and the United States -- plus Germany.

It is designed to lay the groundwork for a meeting of foreign ministers of the world body in New York next Tuesday.

The international standoff over Iran's nuclear ambitions worsened when it failed to comply with a UN deadline last Friday to suspend uranium enrichment, which makes the fuel for civilian reactors but what can also be the explosive core of bombs.

A French foreign ministry spokesman confirmed that the EU three, which had held months of ultimately fruitless negotiations with Iran, backed a resolution that would give "binding force" to the international community's demands.

But while the Western countries put out a hard line, reflecting their fear that Iran is working toward building a nuclear arsenal, Russia and China have signalled opposition and are seeking a more diplomatic approach.

Iranian Foreign Minister Manuchehr Mottaki expressed confidence that those two veto-wielding countries, which are important trading partners, would block a resolution with UN sanctions.

"There is a very wrong assumption held by some that the West can do anything it wants through the Security Council," he told the hardline Tehran daily Kayhan.

Mottaki insisted there was no question, "absolutely not," of Iran returning to a freeze of its uranium enrichment work.

Also Tuesday, the head of the country's Atomic Energy Organis-ation, Gholam Reza Aghazadeh, told the ISNA student news agency that Iran had succeeded in enriching uranium to a higher level of purity than previously achieved.

But he said the grade reached -- 4.8 percent purity -- would not be exceeded because "this level suffices for making nuclear fuel".

The clerical regime has insisted its nuclear activities are exclusively for developing atomic energy.

Purity of more than 90 percent is required to produce the fissile core of an atom bomb -- a weapon Western intelligence assessments say Iran is at least seven years from being able to build.

With a UN consensus on how to tackle the sensitive issue far from assured, several US media have speculated Washington might decide to launch airstrikes on Iranian nuclear targets without UN permission.

US President George W. Bush has declined to exclude the military option and the New Yorker magazine said the use of small nuclear bunker-busters bombs was being considered.

Burns, the US Under Secretary for Political Affairs, said in his briefing with reporters in Paris that "the United States is not taking options off the table".

"We have not lost hope in diplomacy ... (but) we are not going to accept a nuclear weapons future" for Iran, he said.