David Cameron has dismissed concerns that Britons might not be behind the Olympics, saying the Games were a great moment for the UK to come together.
The Prime Minister said the enthusiasm which had greeted the torch relay over the last two months showed they were not a London Games, not an England Games, but a United Kingdom Games.
His comments came after US presidential hopeful Mitt Romney said there were "disconcerting" signs ahead of the Olympics and questioned whether the British people were behind the event.
Mr Cameron said: "Let's put our best foot forward, we're an amazing country with fantastic things to offer. This is a great moment for us, let's seize it."
Speaking in front of the Olympic Stadium where Friday's opening ceremony will take place, Mr Cameron said: "The worries we all have are the great hopes and fears. Our fingers are crossed for everything from the events to the weather to the transport infrastructure and everything else.
"But, from where I stand, I think we're set for a really remarkable few weeks for Britain, when we welcome the world, say this is a great country to come, enjoy the Olympics, but also think of all the other things we've got to offer."
He went on: "Of course, this is a time of some economic difficulty for the UK, everybody knows that. But look at what we're capable of achieving as a nation, even at a difficult economic time.
"In terms of the country coming together, I think the torch relay really demonstrates that this is not a London Games, this is not an England Games, this is a United Kingdom Games."
Mr Cameron went on: "I think we'll show the whole world not just that we've come together as a United Kingdom, but also we're extremely good at welcoming people from across the world."
He said every effort would be made to ensure mistakes such as Wednesday night's flag mix-up never happen again. The PM said the error in which the South Korean flag was wrongly shown instead of that of its sworn enemy, North Korea, at a football game was "an honest mistake".