British Prime Minister David Cameron delivered his "welcome" speech to international media on the 100-day countdown on Wednesday to the 2012 London Olympic Games.

"In just 100 days time, the 2012 Olympics will open in London - a spectacular start to the greatest show on earth ... and that's why my message to you today is this: welcome," said Cameron.

The Prime Minister pledged that Britain will stage "the best Olympics ever" this summer when they are "also celebrating the 60-year reign of Her Majesty the Queen - the second longest-serving monarch on the planet."

"Britain will be looking its best. We've built brilliant new venues - on time and within budget. We've got our city ready, our transport systems in place, and we are looking forward to welcoming the world," said the Prime Minister.

"These games are about two things ... Sport will be at the heart of this great competition. We will see world records broken, memories created and new friendships begun ... When the Games are over and the medals handed out, these Olympics will go on changing lives for the better."

London is the only city to be awarded the Olympics three times.

In 1908, the modern Olympics came to London where Olympic athletes paraded under their national flags for the first time.

Then, in 1948, London again hosted the Games in the shadow of a devastating world war, bringing countries together to celebrate the Olympic ideals of friendship and international community.

For the Games this summer, Britain has regenerated a whole new quarter of London around the Olympic Park in the east of the city, invested in new sporting facilities and established a new School Games' competition in schools all around the country.

"The legacy of London 2012 is not limited to the Britain. The International Inspiration programme is creating opportunities for more than 12 million people in 20 countries around the world ...

"Hosting the London 2012 Games is a tremendous honour. We want to make it a great moment for Britain, and we are looking forward to welcoming the world to be part of it," said the British Prime Minister.