Barack Obama, the Democratic presidential nominee, said on Thursday night that the troop surge in Iraq had succeeded beyond his – or anyone else’s – expectations, adding that he believed the US was fighting a war on terror.

Mr Obama’s comments, in an interview with Fox News – a channel which his campaign has clashed with in the past – come after months in which he has consistently outlined his opposition to the surge, which he has described as a tactical success imposed on a strategic blunder.