Speaking, ironically, to employees of BAE Systems Inc, the US subsidiary of the British defence company, in the elegant New England town of Nashua on Monday, Mr Romney said that America was at a crossroads in history.

"The question is whether we're going to become a stronger nation leading the world or whether we're going to follow the path of Europe and become a second-tier military and a second-tier nation." European countries had chosen to "become a wonderful nation but not the world's power".

America's health system should remain privately rather than government run, he insisted. "I do not want to go the way of England and Canada when it comes to healthcare," he said.