This week brings two tests of whether the United Nations can do much about nuclear proliferation. The first and showiest is the competition of insults and threats at the General Assembly in New York. The second, low key and technical, is in Vienna today, when the International Atomic Energy Agency (IAEA), the UN’s watchdog, will discuss detailed and pointed complaints about Iran and North Korea. Both are likely to reveal the dwindling constituency for curbing Iran.

In New York, this week is theatre. Sarah Palin and Hillary Clinton have removed themselves from the rally called to yell at Mahmoud Ahmadinejad, the Iranian President, but most of the formal speeches are of a similarly noisy nature. On the subject of Iran they are largely vacuous, not for lack of seriousness, but because the diplomatic options are disappearing.

There are three changes that make the outlook for curbing proliferation gloomier than it was even at the start of this year. The first is Russia’s new hostility to the US and Europe. At meetings on Iran last week, among the six countries that have been most involved in trying to persuade it to curb the programme, Russian officials were resistant to more sanctions. The US and Europe believe the programme conceals weapons ambitions, despite denials from Iran.

The second is that North Korea may be going back on its much praised decision in February 2007 to freeze its nuclear weapons programme. Last week it asked the IAEA to unseal equipment at its nuclear reprocessing plant, which separates plutonium for weapons from reactor waste. This appears to represent a new, uncompromising line by senior officials amid uncertainty about whether Kim Jong Il, the leader, is seriously ill. At the least, this needs an urgent diplomatic assault to try to convince officials of the value of the original bargain: abandoning nuclear work in return for aid and contact.

The US has inflicted the third setback on itself through its new pact to help India with nuclear technology. By failing to insist that India comes within the Nuclear NonProliferation Treaty or on proper checks to prevent US help being used for military purposes, it undermines the treaty. Iran can retort that there is no reason to comply with the IAEA if others are apparently rewarded for not bothering to sign the treaty at all.

Iran has taken note of these shifts in its favour to conclude, apparently, that it does not have to give an inch in its dealings with the IAEA. In the past six months it has accelerated its programme of uranium enrichment, according to the IAEA.

The tussle between Iran and the IAEA board has now become confrontational, despite the desire of Mohamed ElBaradei, the Director-General of the IAEA, that the tone should stay cool and technical and that the dispute, as far as possible, should be run out of his domain in Vienna, not the UN Security Council in New York. The latest report by the IAEA to its board, however, set out baldly the precise questions about the sources and aims of the programme, which Iran has refused to answer. It did not find evidence of weapons manufacture, but it did find signs of access to weapons design.

The dispute now goes to the 35-nation IAEA board. Its past appetite for censuring Iran, however, has been erratic. The US and Europe need to win solid support there, and in talks in New York, if UNbacked efforts are to retain any momentum. Otherwise they will have to resort to sanctions on their own – not useless, but a poor second best.

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