London begins 100-day countdown to Olympics 2012

London Olympic organisers stressed the importance of creating a legacy from the Games on Wednesday as they started the 100-day countdown by unveiling the event's motto: "Inspire a generation".

The milestone was marked by celebrations around the world as well as the start of three test events to iron out any operational problems before the opening ceremony on July 27, and Olympic bosses insisted London was ready.

"Expectations are high, and we won't disappoint," said former Olympic gold medallist and London Games chairman Sebastian Coe.

He was speaking at the Royal Botanic Gardens in Kew, southwest London, where 20,000 flowers were planted on Wednesday in the shape and colours of the five Olympic rings. They are visible from planes flying into London Heathrow Airport.

"The London 2012 Olympics and Paralympics are within touching distance now and there's something incredibly exciting about that," added Culture Secretary Jeremy Hunt, the government minister with responsibility for the Games.

"The country is getting ready to welcome the world this summer and it's set to be an amazing celebration that we will never forget."

Some 31 out of 42 sports test events have been completed so far, with dress rehearsals for wheelchair rugby, synchronised swimming and shooting all starting on Wednesday.

Amid the all-round air of optimism, Paul Deighton, the London Games chief executive, stressed that there was still an "enormous amount to do", with several temporary venues to be completed. Some 200,000 temporary seats are yet to go in.

Olympic fever will spread beyond Britain's borders as sports fans around the globe join in the countdown.

In the United States, former heavyweight boxing champion Lennox Lewis will lead 100 cyclists and an open-top London double-decker bus on a ride down Miami's South Beach.

Events were also taking place in Istanbul, Caracas, Wellington, Berlin, Sarajevo, St. Petersburg and the Palestinian Territories.

"There is a groundswell of support and excitement, not just in the UK, but internationally as the final countdown to the London 2012 Olympic Games begins," Coe said.

"Whether it's the competing athletes or people getting ready to join their communities in supporting torchbearers on the streets of the UK, the whole world is getting ready for London."

Queen Elizabeth II will open the Games at a lavish ceremony at the Olympic Stadium in Stratford, east London, on July 27, preceded by fly-past displays by the Red Arrows, the Royal Air Force's acrobatics team.

London will be the first city in the modern era to host the Olympics three times, having already held them in 1908 and 1948, and hopes the event will give the ailing British economy a much-needed boost.

Despite a budget of £9.3 billion ($14.8 billion, 11.2 billion euros), organisers have long accepted that they cannot match the spectacle provided by the 2008 Beijing Olympics.

But they hope the opening and closing ceremonies will bring together the country's most creative minds to produce a celebration of Britishness.

Organisers have also promised to create a lasting legacy from the Games -- the vow was a key part of their bid for the event back in 2005, and is now reflected in the official motto.

Despite the confidence of the team behind the Games, doubts remain about how London's already stretched transport system will cope with ferrying spectators and athletes around the congested capital.

Security has also cast a shadow since the day after London won the bid, when suicide bombers killed 52 people on the public transport system.

More than 40,000 soldiers, police and private security guards will be mobilised to try to prevent incidents such as the hostage-taking of Israeli athletes at the 1972 Munich Olympics and the bombing of the 2004 Atlanta Games.

Stressing that the threat of terrorism was nothing new to London, sports minister Hugh Robertson said: "I'm absolutely as confident as I possibly can be 100 days out that we will deliver a safe and secure Games."