Anne Penketh: Why scrapping the shield could be the best defence against Iran

President Barack Obama's decision to bow to the inevitable by scrapping his predecessor's plans for the missile defence systems in Poland and the Czech Republic highlights the break with the Bush doctrine and a return to a more multilateral approach in US foreign policy. The Nato secretary-general, Anders Fogh Rasmussen, welcomed the move as a "positive step", and it is clear the Alliance has been kept in the picture about the administration's thinking, which may involve Turkey, given its strategic border with Iran.

Mr Obama's decision could also contribute to greater cohesion within Nato by removing a major irritant that had divided eastern and western Europe.

The President did not define the "new architecture" of the future missile defence system, but his Defence Secretary said that existing sea-based interceptors would be part of the mix and would provide a "better missile defence capability" that could be deployed earlier than the Bush plan envisaged.

Obama aides have few illusions that Iran will heed UN demands to give up its uranium enrichment programme which Western governments fear is the first step towards a nuclear weapon. If Tehran overcomes technical problems it could "break out" of the UN-supervised regime to produce sufficient weapons-grade uranium for a bomb early next year.

So the US administration is coupling a continued offer of dialogue – with talks to be held between the big powers and Iran on 1 October – with talk of increased financial sanctions and the reconfigured missile shield as part of a containment policy.

If Russia and China continue to block expanded UN sanctions, then the US would look to Britain, France and Germany to target Iranian banks. The question remains whether Israel would wait that long until taking military action against Iran.

There is also considerable debate about the effectiveness of sanctions, which could bolster the Iranian black market and strengthen the powerful Revolutionary Guards, whose tentacles stretch across the Iranian economy.

The writer is Washington Program Director for the British American Security Information Council (BASIC)