A UN official said referral could be requested by any country or group of UN member states or by the UN secretary general.

But in order to approve the request, council members must be persuaded that the issue is a threat to international peace and security and that the council is the appropriate venue for tackling it.

For the moment, the Iranian nuclear issue is being handled by the Vienna-based UN nuclear watchdog, the International Atomic Energy Agency (IAEA), and its board has to decide whether to refer Iran to the Security Council.

British Prime Minister Tony Blair said an emergency meeting Thursday of an EU troika in Berlin would weigh up its response to the crisis but it was "likely" to end in Iran's referral to the Security Council, as a prelude to possible UN sanctions.

His comments followed Tehran's announcement Tuesday that it was ending a two-year suspension of nuclear fuel research, a decision which triggered a furious reaction from the United States, the European Union and a host of other countries.

Europe and the United States fear that Iran's nuclear program could be a cover for developing atomic weapons, a charge Tehran strongly refutes, saying it is for civilian purposes only.

Any referral would take the form of a letter from IAEA chief Mohamed ElBaradei to UN Secretary General Kofi Annan, who would then relay it to the current Security Council president, Tanzania's UN envoy Augustine Mahiga.

The council president would then have to consult his 14 colleagues before putting the issue on the agenda.

A UN source said the preference is for consensus, but a member -- even one of the five veto-wielding permanent members (Britain, China, France, Russia and the United States) -- would find it hard to block putting the issue on the agenda if the other 14 chose to do so, as there is no veto on procedural matters.

Tasked with maintaining international peace and security in accordance with the UN charter, the council is the only UN organ with the power to make decisions that all member states are required under the charter to accept and uphold.

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