Leading article: Time for a new approach in an effort to end this stand-off with Iran

It is now more than a week since Iran captured 15 British service personnel in the Persian Gulf. All the claims and counter-claims from British and Iranian military spokesmen this week over whether this incident took place in Iraqi or Iranian territorial waters are something of an irrelevance. There is never likely to be conclusive proof, accepted by both sides, of who was really trespassing. The most important question is how the situation can be defused and the return of the captured personnel secured.

It has been suggested that Britain has played it wrong diplomatically over the past seven days. Some former diplomats feel Britain went to the UN Security Council for a condemnation of the Iranians too soon, and that this should have been held in reserve until all other avenues of pressure had failed. Referring the issue to the UN certainly seems to have angered the Iranians, who, on getting wind of the Security Council's statement that expresses "grave concern" at Iran's actions, announced they would not be releasing early the sole female captive, Leading Seaman Faye Turney, after all.

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But there is a bigger problem here than clumsy diplomacy. Quite simply, Iran is holding most of the cards. Because of the catastrophe in Iraq, the UK has no real diplomatic leverage in the region. Tony Blair calls the Iranian action illegal in international law and cites the United Nations mandate for the presence of British forces in Iraq. But the US and Britain invaded Iraq ignoring the will of the UN. The former UN secretary general, Kofi Annan, called the action illegal. Mr Blair has little moral authority when he cites international law now. It is notable that the UN statement stopped short of deploring the Iranian action, as requested by Britain. It also makes no mention of Security Council resolution 1723 that authorises the coalition presence in Iraq. The wounds opened by the foolish invasion of Iraq by the US and the UK have not healed.

The American sabre-rattling over Iran's nuclear programme has raised the stakes, too. It is increasingly clear from the preposterous letters that Ms Turney has been forced to write that hardline elements in Tehran want to use this incident as part of a wider propaganda war against Britain and America. But we also ignore Tehran's paranoia at our peril. British ministers never mention that US forces have Iranian territory more or less surrounded. America is in Iraq, Afghanistan and recently they have moved two aircraft carriers to the Gulf.

If there is to be a way out of this mess, it may well come with the help of the European Union. The EU still has leverage and diplomatic links with Iran. Brussels is more respected in Tehran than Britain, the US or the UN. It also has considerable economic leverage. The EU is Iran's biggest trading partner, accounting for more than 40 per cent of its imports. Much of this trade is also underpinned by export credit guarantees from European governments. The EU's response to the crisis has so far been solid, but not particularly impressive. Angela Merkel, the German Chancellor, who currently holds the leadership of the EU, has expressed her desire to see the personnel released. The EU's foreign policy chief, Javier Solana, called on Iran to release the sailors immediately and said Iran had made a "big mistake". Other EU foreign ministers expressed their solidarity with Britain at a meeting in Germany yesterday. But they were wary of threatening a trade freeze.

The crisis is at a sensitive stage. European leaders are right to be wary of inflaming the situation further. But caution must not become passivity. This should be a question of European solidarity. Unless these sailors are released soon, the EU must set about making the full weight of its influence felt in Tehran.