Curtain up on London's Olympic showpiece

Costing £9.3 billion ($14.5 billion) and featuring more than 10,000 athletes, the four-yearly sporting extravaganza will open officially after a rollercoaster build-up.

Seven years after London defeated Paris for the right to host the 2012 showpiece, the curtain goes up on superstars such as Usain Bolt, Michael Phelps and Roger Federer as well as an army of ambitious amateurs.

Iconic venues and landmarks such as Wimbledon, Lord's and Hyde Park will form the backdrop to the Games while the Olympic Park complex, hosting swimming and athletics, has transformed a previously derelict part of east London.

"We made five promises with the bid, among them to place athletes at the centre of the project, to create a magical atmosphere, to inspire the youth of the world and to leave a lasting legacy," said Games chief Sebastian Coe.

"It has been an extraordinary journey over seven years."

The opening ceremony, starting at 2000 GMT and expected to be watched by 80,000 spectators and billions worldwide, is being staged by Oscar-winning British movie director Danny Boyle.

His fellow film-maker Stephen Daldry, the ceremony's creative director, said the show would highlight "the rich heritage, diversity, energy, inventiveness, wit and creativity that truly defines the British Isles."

Jamaican track star Bolt insists he is "ready to go" in his bid to defend his double sprint titles.

"I'm always ready," said Bolt, who will carry his country's flag at the opening ceremony. "I've had slight problems, but I'm ready to go."

Fitness concerns, an early morning car crash and losing over both the 100m and 200m to compatriot Yohan Blake in the Jamaican Olympic trials raised serious doubts about Bolt's ability to defend his titles.

In the pool, Phelps, whose eight golds in Beijing took his overall medal tally to 16, needs three more to surpass the all-time record of 18 set by Soviet gymnast Larisa Latynina between 1956 and 1964.

His seven-event programme gives him plenty of room to make more Games history and anchor a US team determined to continue its dominance against Australia and China.

Phelps is the two-time defending champion in all four of his individual events -- the 100m and 200m butterfly and 200m and 400m individual medley.

One of his biggest challengers is team-mate Ryan Lochte, who has emerged as a serious threat in both medleys.

Australia is bringing in the big artillery with James "The Missile" Magnussen and James "The Rocket" Roberts, in the prestigious 100m freestyle.

Magnussen is the 100m free world champion and the fastest man ever in a textile suit with a 47.10sec.

The US have a "Missile" of their own, however, in 17-year-old Missy Franklin, who is set to become the first US woman to swim seven events at one Games.

South Africa's Oscar Pistorius, known as 'Blade Runner' because he runs with carbon fibre prosthetic running blades, will make history as the first double amputee athlete to compete at an Olympics.

At the velodrome, Bradley Wiggins, fresh from his historic Tour de France triumph, will fire up home hopes.

Zara Phillips, the granddaughter of Queen Elizabeth, adds a royal lustre to the equestrian events at Greenwich.

Federer, having won a record-equalling seventh Wimbledon title, returns to the All England Club in southwest London looking to add singles gold to the doubles he won with Swiss compatriot Stanislas Wawrinka four years ago.

His rivals will be Djokovic and Andy Murray but there will be no defending champion Rafael Nadal, who pulled out to rest his ongoing knee problems.

The United States will be comfortable favourites in the men's basketball with a Dream Team boasting LeBron James and Kobe Bryant.

The final week of build-up to the Games has endured a number of embarrassing setbacks, most of which have involved mix-ups over nationalities.

North Korea's women's football team walked off the pitch at Glasgow's Hampden Park in protest at their players' photos appearing next to flags of South Korea.