Michelle Obama will add her backing to Team USA today as she begins a trip to the capital in support of the London Olympics.
The US First Lady will meet her nation's Olympians in an event at their east London training ground, before holding an event for 1,000 children aimed at boosting their interest in the Games.
Mrs Obama is leading the US presidential delegation which includes a ringside seat at the opening ceremony.
She begins her visit this morning at the University of East London, where she will offer her support to athletes at an informal breakfast.
Later she will host a sporting event - called Let's Move! - at the US ambassador's residence in central London for about 1,000 US military children plus US and British students.
Let's Move! is an initiative created by the First Lady in a drive to combat childhood obesity within a generation.
David Beckham and Manchester United stars are also set to appear at the event, as well as Mark Ronson, Katy B and The Wanted - with SpongeBob SquarePants and the Power Rangers on hand to entertain the children.
Former gymnast Nadia Comaneci, ex-sprinter Carl Lewis and members of the US track and field team who will be competing at London 2012 are among the line-up of famous sporting faces set to attend.
It is hoped the sports stations provided by Nickelodeon, the NBA and USA Basketball, US Tennis Association, USA Field Hockey, USA Track and Field, Manchester United and Right to Play will help the youngsters get active.
Earlier this week Mrs Obama said coming to London for the Olympics was "a dream come true" and said she was "beyond proud" to be leading the delegation.
"If anybody had asked me when I was 10 or 11, or actually 40, whether I would have been doing this, I would have bet not," she said.
"Some of my fondest memories when I was young and not so young involved watching the Olympics on TV and cheering on Team USA."
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Tonight she will attend a Buckingham Palace reception for heads of state, hosted by the Queen, with whom she struck up a warm friendship on previous visits.
On Saturday the US delegation is spearheading an Olympic fun day to allow US youngsters to cheer on their athletes in London and try out different sports in their neighbourhoods.
Mrs Obama said: "I am very excited about this trip for so many reasons but I am excited that it will serve as a powerful opportunity to send another message to the kids in this country and other countries about the importance of staying fit, learning to compete and staying healthy.
"This is not just about sports, this is about being active."
