The Olympics will boost the UK economy by £13bn over the next four years, the Prime Minister will say today.
In a speech in the East Midlands, David Cameron is expected to say the country is set for an "outstanding" Games
His comments come as athletes from around the world begin to arrive in the UK ahead of the event's opening ceremony on July 27.
But Mr Cameron will stress that the Olympics and Paralympics will be an opportunity to "boost Britain" by selling it to the rest of the world.
"They should be great for our economy," he said.
"We shouldn't see them as an expensive luxury in tough times - it is precisely because times are tough that we have got to get everything we can out of them to support jobs and growth in the economy."
He will add: "I am confident that we can derive over £13bn benefit to the UK economy over the next four years as a result of hosting the games.
"I am certain that when you add in the benefits from construction the total gain will be even greater."
He hopes that the economic benefits will be worth "more than the cost of holding the games in the first place".
The Government estimates that 4.5 million extra people will visit the UK after the Games, contributing to over £2bn worth of spending from extra tourism.
Mr Cameron is also expected to promote the Olympic Park in Stratford, saying it was built on time and under budget, and is "ready and looking stunning".
The venue is seen as "a great showcase for British design, engineering and project management", he will say, and has boosted the reputation of the British construction industry
He will point to a strong legacy from the project - the transformation of East London - but stress that the UK also needs to secure legacy for both sport and volunteering after the event.
Meanwhile, a study by Lloyds Banking Group said the Games would benefit the UK economy to the tune of £16.5bn.