Prime Minister David Cameron insisted on Thursday that Britain would deliver a memorable Olympics after US presidential hopeful Mitt Romney backtracked on barbed comments he made about the London Games.
On the eve of the opening ceremony, the anticipation built as Prince William and his wife Catherine were among tens of thousands of spectators as the Olympic flame was brought to Buckingham Palace.
But Romney, in London to attend Friday's opening of the Games, said the preparations had been "disconcerting", pointing to the failure of a private security contractor to provide the number of guards it had promised.
The Republican candidate also wondered aloud whether the British public would get behind the first Games to be held here since 1948.
On the eve of the Olympics, Cameron said security "matters more than anything else", and said he was convinced the Games would prove that Britain could stage a world-class event.
Cameron also said he was sure Britons would get behind the Games despite an economic downturn — and took an apparent swipe at Romney's past as head of the 2002 Winter Olympics in Salt Lake City.
"We are holding an Olympic Games in one of the busiest, most active, bustling cities anywhere in the world," Cameron said.
"Of course it's easier if you hold an Olympic Games in the middle of nowhere."
Cameron said he would take personal responsibility for the security of the Games, which are guarded by Britain's biggest ever peacetime force.
Britain has deployed an additional 4700 troops in recent days to make up the shortfall in guards supplied by giant contractor G4S, taking the total military deployment to 18 200.
"I think we've made as many preparations as we can. I think we have very good contingency plans in place," Cameron said at a press conference with chief Games organiser Sebastian Coe in front of the Olympic Stadium in east London.
Romney told NBC News on Wednesday that "the stories about the private security firm not having enough people, the supposed strike of the immigration and customs officials — that obviously is not something which is encouraging".
It was "hard to know just how well it will turn out", he added.
But he struck a more diplomatic note after talks with Cameron later.
"I am very delighted with the prospects of a highly successful Olympic Games," Romney said.
"What I have seen shows imagination and forethought and a lot of organisation. I expect the Games to be highly successful."
The US team meanwhile seemed happy with the conditions in London.
"Our experience has been nothing but positive," said Scott Blackmun, US Olympic Committee chief executive officer.
"We're not seeing any indication of anything less than great enthusiasm from people on the street."