Signal comes as new round of negotiations on Tehran's nuclear programme gets under way in Moscow

The EU has said it has no plans to postpone its imminent oil embargo on Iran as a new round of negotiations on Tehran's nuclear programme gets under way in Moscow.

The talks started at 11am Moscow time (8am BST) with a plenary meeting between an Iranian delegation led by Saeed Jalili, the secretary of Iran's Supreme National Security Council, and a six-nation group of negotiators from the US, UK, France, Germany, Russia and China.

A spokesman for Catherine Ashton, the EU foreign policy chief who acts as convenor for the group, said it expected the Iranians to maintain a solid negotiating position.

The spokesman, Michael Mann, said: "As far as we are concerned, we have put forward a concrete set of proposals; the Iranians have raised a set of ideas and issues.

"Mr Jalili said on the phone last week that he was prepared to seriously engage with our proposals, so we want to hear what he says. We have to move forward at these talks … There is no point in having talks for talks' sake."

At the last round of negotiations, last month in Baghdad, the six powers proposed a deal under which Iran would stop the production of 20%-enriched uranium, a particular proliferation concern, ship at least some of its 20% uranium stockpile out of the country, and halt operations at its underground enrichment plant Fordow. In return, it would get fabricated uranium fuel plates for a medical research reactor, help with nuclear safety, and spare parts for its commercial fleet of airliners.

Jalili did not respond to the proposal, but Iranian officials briefed journalists that the package was unacceptable. There had been reports in Washington that the US wanted to try negotiating a comprehensive agreement in Moscow rather than piecemeal confidence-building measures, but Mann said the six-nation offer was unchanged.

"What is on the table here is what was on at Baghdad," he said, adding that the EU was not offering to postpone its oil embargo, which is due to take effect on 1 July. "It is a piece of law, agreed by all 27 members of the European Union."

However, he added that if the talks gathered momentum, there could be reciprocal steps that could match further concessions by each side.

Arriving at the talks, the Russian negotiator on the six-nation group, deputy foreign minister Sergei Ryabkov, repeated Moscow's longstanding opposition to unilateral sanctions, but he also stressed the need for Iran to set out concrete proposals on its 20% enrichment and on the Fordow plant.

Tehran's Press TV quoted Jalili as urging the west "to respect Tehran's nuclear rights in order for the Moscow meeting to succeed". The remark is a reference to Iran's longstanding demand that the international community recognise its right to enrich uranium in principle.

Mann said the right to enrich uranium was not specifically mentioned in the Non-Proliferation Treaty, and that the UN security council has passed several resolutions calling on Iran to suspend enrichment until it has assured the international community of its peaceful intentions.

The already modest expectations for the Moscow talks were lowered further when Iranian diplomats arrived criticising preparations for the negotiations, saying that the six-nation group had "wasted a month" since the Baghdad round. Tehran had wanted preliminary technical meetings to agree an agenda, but Ashton's office insisted there had been enough discussion about the process and preferred to talk only about the substance of a deal.

A breakdown in the talks would make military action by Israel more likely, but western officials said they were not prepared to continue unless Iran showed a real willingness to bargain over its enrichment programme.