Not one, but many nations suffered in the terror attacks on the US. During a visit to Ground Zero at the World Trade Centre, UN Secretary-General Kofi Annan said: "I don't have the exact number, but I understand that 62 countries have lost nationals here in this disaster. This is why I said that no one can remain indifferent." The shock and revulsion of the international community was reflected in UN Security Council resolution 1368 which was unanimously adopted the day after the tragic events. In an institution where language and rhetoric matter because they can lead to, or give implicit sanction for, military or other forms of action, the strength of this resolution was both remarkable and significant.

The attack on New York and Washington was categorised as "a threat to international peace and security". The maintenance of international peace and security is the primary responsibility of the Security Council, acting on behalf of the entire UN membership, so there can be no doubt over the seriousness with which the attack was viewed by the council.

The text had the backing of Russia and China, whose support for pro-US resolutions can never be automatically assumed. It called for increased co-operation between states to "prevent and suppress" terrorist acts. The council declared its readiness "to take all necessary steps to respond to the terrorist attacks".

According to UN sources: "There really was a very, very strong sense of rage throughout the Security Council as well as an empathy and solidarity with the Americans." In his statement to the council on the attacks the head of the Irish mission at the UN, Mr Richard Ryan, said those responsible "must be brought to justice and the entire international community must work together towards this end".

At least for the moment, the international community stands as one against the terrorist threat but the question is, how long can this impressive unity be maintained? Ireland takes over the presidency of the council for a month from October 1st and maintaining international solidarity on this issue will now be one of the primary tasks facing the Irish delegation.

At time of writing, the precise US response to the New York and Washington attacks remains unclear. Having obtained a very strong resolution of support within 24 hours of the events, the US can be fairly confident that the Security Council would give its approval in advance or retrospectively to a measured and precise military response directed against a legitimate target. It appears that the US wishes to act in concert with other nations but there is also provision in the UN Charter for it to take unilateral action, since Article 51 guarantees "the inherent right of individual or collective self-defence if an armed attack occurs against a member of the United Nations".

Whereas the United Nations itself has the right to wage war under the charter, in practice it would be more likely to authorise member-states to do so in the UN's name. Should the US seek such a mandate in the near future it could very well be granted but, given the nature of international power politics, a delay of a few weeks would probably see a falling-off in support. Therefore any request for a mandate would need to come sooner rather than later. Secondly, experienced UN hands warn that the wider the military campaign and the greater the number of civilian casualties, then the harder it is to keep an international coalition together.

For the present, however, the Americans are in the driving seat and a fair degree of leeway will be granted. But there is still a good deal of uncertainty about US intentions. "Do they want to inform or get clearance from the Security Council and will it be before or after they take action?" a senior diplomat wondered. Alternatively, there could be an initiative by another member of the council, perhaps acting as an unofficial proxy for the Americans.

Brian Cowen will travel to the US next week, heading first for Washington and then to New York and the UN building on the East River. He will be involved closely in deliberations leading up to the start of the Irish presidency and may even personally chair a meeting of the council in early October. He was originally scheduled to address the General Assembly but although the assembly is formally in session, the two-week "general debate" that was to have begun on Monday with a speech by President Bush has now been postponed for security reasons.

Ireland had an ambitious programme for its presidency and was planning to highlight a number of topics known in diplomatic jargon as "big-ticket issues". How this agenda will be affected by the recent cataclysm remains to be seen but it will be surprising if the Irish presidency does not focus attention on the problems of the Democratic Republic of the Congo, Somalia, Burundi and East Timor, among others. Afghanistan, where UN sanctions against the Taliban regime have been in operation for some time, was due to come up at the council anyway. It would be surprising if the Middle East did not feature in some shape or form.

But for the moment, the terrorism issue displaces all others in the public mind. The council has called on Afghanistan's Taliban rulers to hand over the alleged terror mastermind, Osama bin Laden, and close all terrorist training camps "immediately and unconditionally". The Security Council imposed sanctions on Afghanistan in November 1999 to put pressure on the Taliban to turn over bin Laden to face charges over bomb attacks on US embassies. It added an arms embargo last January.

China, which is one of the five permanent members who hold a veto over the Security Council, gave its conditions for supporting military retaliation: "An attack on terrorists must be based on concrete evidence and have clear-cut objectives without endangering innocent people."

The position of Russia -- another member of the Permanent Five -- is not dissimilar and a spokesman said: "We have come to mutual agreement that we need to react to terrorist acts, but this reaction must be within the framework of international law. And when resorting to certain actions in response to terrorist acts we should make sure that the civilian population does not suffer."

Ireland is a more consistent ally of the US and the Taoiseach has pledged that Ireland "will play its part to the fullest" in addressing the challenge of international terrorism. At the same time he expressed confidence that the US understood any response had to be "proportionate, measured and focused on the pursuit of justice".

Even Bertie Ahern is not giving the US a blank cheque and the challenge for the Irish presidency of the Security Council will be to help ensure that the right of the US to self-defence is exercised in a manner which is consistent with the overall interests of the international community.