Tehran today ruled out freezing its uranium enrichment programme, casting doubt over the value of talks between Iran and six world powers less then an hour after they started.

The talks — with the US in attendance for the first time — had raised expectations of possible compromise on a formula under which Iran would agree to stop expanding its enrichment activities. In exchange, the six powers — including the five permanent UN Security Council members — would hold off on passing new UN sanctions against the Islamic Republic.

But the comments from Keyvan Imani, a member of the Iranian delegation, appeared to indicate that Tehran was not prepared to budge on enrichment.

"Suspension — there is no chance for that," he said in the courtyard of Geneva's City Hall and venue for the convention.

"As our supreme leader (Ayatollah Ali Khamenei) clearly said, our path is very clear: We are not going to abandon our rights."

The enrichment issue is key because the activity can produce either fuel for nuclear power stations or the material used in the fissile core of warheads. Iran has defied three sets of UN sanctions demanding it cease its programme, saying it has a right to its peaceful uses under the Nuclear Nonproliferation Treaty. But there is growing concern the Islamic Republic might want to build nuclear weapons instead.

The presence of US Undersecretary of State William Burns at the talks — the first instance of the US attending such meetings — had led to hopes of compromise.

Recent Iranian statements suggest Tehran is looking to improve ties with the US, with officials speaking positively of deliberations by the US administration to open an informal diplomatic presence in Tehran after it closed its embassy decades ago.

Although the US says the Geneva talks focus only on the nuclear issue, Iranian Foreign Minister Manouchehr Mottaki said on Friday they could also result in agreements to open a US interest-protection bureau and have direct flights between the two nations.

US interests in Iran are now represented by the Swiss Embassy in Tehran and official contacts between the two countries are extremely rare.

Imani said Tehran had not yet received a proposal from the US on opening a representation but would "study it positively" if it did.

But he downplayed the presence of Burns at the meeting.

"He is (just) a member of the delegation; of the six countries engaging Iran on the nuclear issue," Imani said.

He also denied that the "freeze-for-freeze" formula — a stop to Iranian enrichment growth in exchange for no new UN sanctions — was formally on the agenda of the Geneva talks, saying the two sides were meeting to discuss common points of their diverging plans to ease nuclear tensions.

Chief EU envoy Javier Solana and Iranian negotiator Saeed Jalili left together as the talks broke for lunch, speaking earnestly with each other. Burns followed some time later, accompanied only by an aide. All three declined to answer questions.

The United States and its five partners — Britain, France, China, Russia and Germany — remain committed to getting a full halt to Iranian enrichment.

Still, Burns' decision to attend the Geneva talks shows that Washington may accept "freeze-for-freeze", which is something less than full suspension, at least as a first step.

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