The surprise comments by Iran's top nuclear negotiator marked a notable softening of Tehran's line towards a deal proposed last week by European countries, coming only a day after officials described the offer as "unbalanced."

"The European proposal for an unlimited suspension of uranium enrichment can be implemented, provided it does not contradict the Islamic republic's criteria," Iran's chief nuclear negotiator Hassan Rowhani said on state television.

Three European states offered Iran a deal on Thursday under which Tehran would receive valuable nuclear technology if it indefinitely suspended all uranium enrichment activities, a key stage in the nuclear fuel cycle.

The three countries -- Britain, France and Germany -- hope that if Iran agrees to the deal it will be possible to stave off US demands for the nuclear issue to be sent before the UN Security Council.

The UN's nuclear watchdog -- the International Atomic Energy Agency (IAEA) -- has given Iran a Nov. 25 deadline to allay concerns about its nuclear activities.

Suspension, not permanent halt?

Rowhani made clear that in Tehran's eyes suspending uranium enrichment indefinitely was not the same as imposing a permanent halt on the practice.

The term "unlimited does not mean permanent. The Europeans are talking about an unlimited (suspension) during the negotiations as it is forseen that long-term negotiations are starting with the Europeans," he said.

"They say for example that if the negotiations last seven months, Iran must respect the suspension. We have always said that if the Islamic republic accepts the suspension at whatever level, this will be a voluntary decision."

Depending on the level of purification, enriched uranium can be used either as fuel for a civilian reactor or as the explosive core of a nuclear bomb. Iran strongly rejects US accusations it is seeking to manufacture atomic weapons.

EU must recognize Iranian sovereignty

Rowhani said Tehran would continue cooperating with the international community but insisted that European nations must also recognise its right to civilian nuclear technology, according to the official IRNA news agency.

"The Europeans must accept that our red lines and national rights cannot be violated," he said.

But his remarks appeared to strike a remarkably conciliatory tone and are likely to be welcomed by the three European heavyweights ahead of a meeting this week to hear the Islamic republic's response to the offer.

"Iran's patience to establish confidence with the world is great," Rowhani said."It will not be exhausted at this early stage. We will calmly continue to work at winning confidence. We are going to carry out any necessary action to create confidence as we want to work with the world in the areas of politics, economy, society and culture and we do not want to worry the world unnecessarily."

Rowhani said the European proposal recognized the rights of Iran under the Nuclear Non-Proliferation Treaty, notably "the right of Iran to possess nuclear power stations."

"Iran has as many rights as a European country under the NPT," he added.

Rowhani vowed that Iran would continue cooperation with the IAEA, "not to make the Europeans happy but to prove the United States is lying when it says Iran is trying to manufacture a nuclear weapon."