Iran has vowed to press ahead with its nuclear programme, as a key United Nations deadline for it to be halted passed today.

Mahmoud Ahmadinejad, the Iranian President, remained defiant as a 60-day grace period Iran had been given to stop enriching uranium for nuclear fuel ran out.

Speaking in the northern Iranian town of Siahkal, Mr Ahmadinejad was quoted by the student news agency ISNA as saying: "We ... will continue our work to reach our right (to nuclear technology) in the shortest possible time."

He added: "Obtaining this technology is very important for our country’s development and honour. It is worth it to stop other activities for 10 years and focus only on the nuclear issue."

The UN Security Council, which in December banned transfers of technology and expertise to Iran’s nuclear programme, had refused to rule out a broad programme of sanctions if the Islamic Republic refused to comply with its demands by today.

Also speaking yesterday Ali Larijani, the Iranian nuclear negotiator, said the country would not heed the UN deadline to halt its programme - though it would be prepared to take part in negotiations to reassure the West that its programme was for peaceful purposes.

"Iran’s nuclear dossier cannot be resolved through force and pressure," he said, after meeting the UN's nuclear watchdog director in Vienna.

"If the other side expresses concerns about possible deviations of Iran’s activities in the future, we have no objections to settling these concerns at the negotiating table."

Mohamed ElBaradei, the Atomic Energy Agency director, who met Mr Larijani in Vienna, was expected to report to the UN today that Iran had ignored its deadline.

It was unclear how the international community would respond. The Security Council is not expected to take action before the next meeting of the IAEA’s 35-nation board of governors on March 5-9, when the issue will be discussed.

Mr Ahmadinejad's nuclear ambitions, combined with his political stance, have caused alarm in the United States and Europe. He has openly called for the destruction of Israel, and recently held an international conference in Tehran aimed at denying the Holocaust.

The West believes Iran is trying to build a nuclear bomb, but Mr Ahmadinejad and his officials repeatedly claim the programme is only to generate electricity.

Analysts believe Iran has ignored UN demands partly because it calculates that the United States' room for manoeuvre has been hugely damaged by the ongoing conflicts in Afghanistan and Iraq.

However, speaking on BBC Radio 4's Today programme, Richard Perle, a hawkish US political lobbyist who pressed President Bush to go to war with Iraq when chairman of the Republicans' Defence Policy Board Advisory Committee in 2003, said military action could not be ruled out.

"We have to be prepared to consider that, otherwise one of the very important incentives for the Iranians to respond to the United Nations will be lost," he said.

"In time, if nothing interferes with it, they will have a nuclear weapon and they will touch off an arms race in the Middle East that will cause all of us to stay up at night."

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