Iran said Sunday it would not compromise on its nuclear "rights" but asserted it was still studying an international proposal that demands a freeze of sensitive uranium enrichment work.
"We are definitely not going to compromise on our rights. We are going to act according to our responsibilities and rights. We are holding the initiative," foreign ministry spokesman Hamid Reza Asefi told reporters.
He was repeatedly asked whether Iran would return to a suspension of enrichment, but only said that "we will not negotiate our right. We will not give up our right."
Asefi declined to categorically say if Iran would reject or accept an international offer of incentives if it agrees to stop enrichment - a process at the centre of fears the country could acquire nuclear weapons.
According to Asefi, the package - drawn up by Britain, France and Germany and backed by the United States, Russia and China - contained elements which were "acceptable" and others which were not.
"As soon as we received it, we opened it and started to study it. We categorised the points. Some of them are acceptable, some have ambiguities, some have to be consolidated, and some of them we don't accept," Asefi said.
Iran's top nuclear negotiator, meanwhile, on a visit to Cairo, told reporters that Tehran would not accept any threats or preconditions in negotiations with the international community.
"The language of threats contradicts the language of negotiations," said Ali Larijani.
US President George W. Bush said Friday that Tehran had "weeks and not months" to accept the proposal to halt its nuclear program and warned that the UN Security Council would act if Iran did not comply.
But Larijani denied that any deadline had been fixed in the proposal and rejected any preconditions. "There is no timeframe We are for negotiations but without preconditions," he said.
Iran has so far refused to suspend enrichment, which can be extended from making civilian reactor fuel to the core of a nuclear weapon. The country argues enrichment for peaceful purposes is a "right" enshrined by the nuclear Non-Proliferation Treaty.
The package was presented to Iran last Tuesday by EU foreign policy chief Javier Solana.
"The Islamic republic of Iran is not trying to buy time, we are trying to come up with an answer that is satisfactory for all sides and we will give our answer after we have meticulously studied the package," Asefi said. His comments came as board members of the UN nuclear watchdog - the International Atomic Energy Agency (IAEA) - prepared to meet in Vienna on Monday.
The IAEA board in February found Iran in violation of non-proliferation safeguards for almost two decades of hiding nuclear activities. This opened the door to possible punitive action by the Security Council.
Seeking a negotiated way out of the impasse, the five permanent members of the Security Council plus Germany have offered Iran a package of benefits if it suspends uranium enrichment and begins talks on guaranteeing it does not seek nuclear weapons.
At the IAEA meeting, a vigorous debate on Iran but no resolution or major initiative is expected.
"The decision to be made is in Tehran, not at the board," a European diplomat told AFP in Vienna. A second diplomat said: "I think that there is no stomach at all from any country next week to posture or stir up any fires at this delicate time in the political process."
Tehran says its nuclear program is to generate electricity but Washington charges this is a cover for developing atomic weapons.
Israeli Prime Minister Ehud Olmert on Sunday expressed hopes that ongoing international efforts to resolve the nuclear crisis with Iran would succeed and urged Tehran to accept a deal.