Opposition by US “hawks” led by Dick Cheney, the vice-president, is complicating efforts by the main European powers to put together an agreed package of incentives aimed at persuading Iran to suspend its nuclear fuel cycle programme, according to diplomats and analysts in Washington.

London is hosting on Wednesday political directors of the “EU3” of France, Germany and the UK, together with China, Russia and the US to look at the twin tools of incentives and sanctions.