Calling nuclear weapons 'disgusting and shameful,' Iranian President Mahmoud Ahmadinejad urged the United Nations to punish countries like the US that threaten to use them.

US Secretary of State Hillary Clinton dismissed Ahmadinejad's comments as the 'same tired, false and sometimes wild accusations' and urged nations to focus on efforts to bring Iran to heel over its nuclear program.

In keeping with past practice during annual UN General Assembly gatherings, the delegations of the US, Britain, France, Germany and others walked out of the chamber during Ahmadinejad's fiery speech.

'The possession of nuclear arms is not a source of pride,' he said at the start of a month-long review conference of the 189 signatories of the 1970 nuclear Non-Proliferation Treaty.

'It is rather disgusting and shameful. And even more shameful is the threat to use, or to use, such weapons.'

Ahmadinejad, the highest-ranking official to attend the conference, called for 'considering any threat to use nuclear weapons or attack against peaceful nuclear facilities as a breach of international peace and security.'

States making such threats should face 'swift reaction' from the United Nations and be ostracized by NPT members.

Clinton later called for similar stiff penalties against countries like Iran that violate their treaty commitments.

'Rules must be binding. Violations must be punished. Words must mean something and the world must stand together to prevent the spread of these weapons,' Clinton said. 'It is time for a strong international response.'

Walkout

The US and its allies accuse Iran of developing the capability to make nuclear weapons under cover of a civilian atomic energy program. Tehran insists it is interested only in generating electricity but has a long record of hiding sensitive nuclear activities from UN inspectors.

The Western walkout came as Ahmadinejad charged that Israel threatened its neighbors with 'terror and invasion' and enjoyed unconditional support from Washington and its allies.

Israel, like nuclear-armed India and Pakistan, never signed the NPT. Israel is presumed to have a sizable nuclear arsenal but neither confirms nor denies its existence.

North Korea withdrew from the NPT in 2003 and conducted atomic tests in 2006 and 2009.

The US nuclear posture review, released last month, reduces the role of atomic weapons in US defense policy but does not rule out their use against countries like Iran and North Korea that are considered to be NPT violators.

Clinton detailed what she described as the strong US record on nuclear non-proliferation and weapons control, including the recently concluded US-Russia deal to cap strategic nuclear weapons and the new US nuclear strategy.

She said the US would ratify nuclear weapons free zones in Africa and the South Pacific and back 'practical measures' to make the Middle East a region free of weapons of mass destruction -- which could pique US ally Israel.

She later told reporters about the Middle East plan that 'the conditions for such a zone do not yet exist.'

Clinton said the US decision to disclose for the first time the overall size of its nuclear arsenal -- 5,113 warheads operationally deployed, kept in active reserve and held in inactive storage -- was proof of greater US transparency.

The total does not include an estimated 4,600 warheads that have been retired and are due to be dismantled.

The Iranian president did not mention his country's uranium enrichment program, which Tehran has refused to suspend, prompting the UN Security Council to impose three rounds of sanctions on Iran.

The US, Britain, France, Germany, Russia and China are now discussing possible new sanctions.

In his speech, UN Secretary-General Ban Ki-moon urged Ahmadinejad to take part in a UN-backed nuclear fuel offer that Iran accepted in October but later balked at. Ban called the deal 'an important confidence-building measure.”

Ahmadinejad denied rejecting it. 'To us, it is an accepted deal,' he said, adding the ball was in the West's court.

Clinton said Iran had shown no sign of accepting the deal.

The US, Britain, France, China and Russia -- the permanent, veto-holding members of the Security Council -- were allowed to keep their nuclear weapons under the NPT but pledged to launch negotiations on scrapping their arsenals.

Non-nuclear weapon states complain the five have not done enough to disarm. – Reuters