“The situation is completely changed. We are a nuclear state,” hardline President Mahmoud Ahmadinejad said in the wake of a breakthrough in the country’s disputed nuclear energy drive, seen in the West as a mask for weapons development.

Iran announced this week that its scientists had successfully enriched uranium to make nuclear fuel.

The Islamic republic insists its programme is peaceful, but the enrichment process can be extended to make the fissile core of a nuclear warhead. The UN Security Council has set April 28 as a deadline for Tehran to halt enrichment.

“We will not negotiate on our rights with anyone,” Ahmadinejad was quoted as saying by the official news agency IRNA. He added that nobody in the country “has the right to step back one iota from the path we are following.”

International Atomic Energy Agency (IAEA) chief Mohamed ElBaradei arrived in Tehran during the night for talks with the regime’s top nuclear negotiator and a message that appeared to be falling on deaf ears.

“We hope to convince Iran to take confidence-building measures including suspension of uranium enrichment activities until outstanding issues are clarified,” ElBaradei told journalists at the airport.

“I would like to see Iran has come to terms with the request of the international community,” adding that he still remained “hopeful the time is right for political solutions, through negotiations.”

ElBaradei must give a report at the end of April on Iran’s nuclear activities to the UN Security Council and the 35 states of the IAEA’s governing council.

Representatives of the five permanent members of the Council plus Germany are to meet in Moscow next Tuesday to discuss the crisis, with the long-running stand-off set to enter a period of far more robust diplomacy.

US Secretary of State Condoleezza Rice called for the 15-member Security Council to take “strong steps” and the White House said sanctions were now an option.

“It’s time for the Security Council to act on the diplomatic front,” said White House spokesman Scott McClellan.

“There are a number of options that are available to us through the diplomatic process,” he said, adding that officials were nonetheless still “pursuing a diplomatic solution”.

Officials from permanent Security Council members Britain, France and Russia, and Germany, all said Iran had taken a “step in the wrong direction”.

Russian Foreign Minister Sergei Lavrov was however quoted as strongly opposing the use of force after US reports over the weekend suggested Washington was considering military action -- even a possible nuclear strike.

“I am convinced that there can be no resolution of the problem through use of force... practically all European countries are in solidarity with Russia,” he said.

But oil-rich Iran has vowed it can weather any sanctions, and -- instead of slamming the brakes on enrichment -- the regime has vowed to accelerate the process and reach an industrial-scale fuel production capacity.

The breakthrough in making fuel was with 164 centrifuges at a pilot plant in Natanz, and a senior official said Iran wanted to install 3,000 centrifuges within the next year.

Ahmadinejad also said Iran wanted to use advanced P2 centrifuges -- devices that are capable of making weapons-grade uranium more efficiently than the P1 technology currently in use in Iran.

“Our centrifuges are the P1 type, and the next step is the P2, which has a capacity four times greater and on which we are presently conducting research,” Ahmadinejad said.