The U.S. first lady told a crowd of young people that the Summer Games are about more than just gold medals — but also urged U.S. athletes in London to strive to claim top prizes all the same.
"Try to have fun. Try to breathe a little bit," Mrs. Obama told American athletes at a breakfast in east London near the Olympic Park.
Obama, who said she was "just in awe" of their company, told the athletes that some of her fondest sports memories stemmed from watching the Olympics on television. She shared the story of her father, who was athletic but contracted multiple sclerosis "in the prime of his life."
"He retained his love of sports, truly," Mrs. Obama said. "And the Olympics was a special time for him to watch amazing athletes of all abilities compete on the world stage."
Among the Olympians attending were two-time fencing gold medallist Mariel Zagunis, who will carry the nation's flag into the opening ceremony, along with the U.S. women's basketball team and track and field members.
"Being here is otherworldly for me," the first lady said. "I am still so inspired."
Later, she was scheduled to attend a reception hosted by Queen Elizabeth II at Buckingham Palace and then go to the London Olympics opening ceremony.
On the vast lawn of Winfield House, the residence of the U.S. ambassador to Britain, Mrs. Obama also joined some 1,000 children — many from U.S. military families based in Britain and others from underprivileged London neighbourhoods — at a sports carnival.
"I'm so excited," Mrs. Obama told the children as a marching band played the University of Florida fight song.
The first lady shared the stage with a host of sports stars, including England's ex-soccer captain David Beckham and U.S. gold medal winners Carl Lewis, Summer Sanders and Brandi Chastain.
Mrs. Obama told the children to draw encouragement from athletes like gymnast Shawn Johnson — who once considered quitting — and from Paralympian Gabe Diaz de Leon, an army veteran who trained to compete in the discus, shot put and javelin after he was paralyzed on operations in Honduras.
"The stories of these athletes remind us that being an Olympian is not just about winning a gold or setting a record. It's about pushing yourself and believing in yourself and refusing to give up," she told the children. "No matter what obstacles you face, keep pushing."
Mrs. Obama later tried out a host of sports alongside the children.
Lewis praised the first lady's "Let's Move!" campaign, which is aimed at tackling childhood obesity and promoting sports.
"She has proven and shown that both she and the president love the Olympics and the Olympic movement," the ex-sprinter said.
While Lewis and other athletes signed autographs, ex-NBA All Star Dikembe Mutombo offered the children tips on basketball. Ex-Manchester United players Peter Schmeichel and Denis Law ran a soccer clinic and members of the U.S. field hockey and tennis squads also ran training sessions.
Ethen Duval, originally from Oklahoma, said was looking forward to the Olympic soccer tournament.
"I can't wait to watch things with my Dad and see the look on his face when something exciting happens and he says 'Wow!'" said the 10-year-old, who lives at Lakenheath U.S. Air Force Base in Britain.
The 46-year-old Mutombo towered above his young pupils.
"They are mostly excited about the basketball (at the Olympics)," he joked.
On Saturday, Mrs. Obama will meet with Samantha Cameron, the wife of British Prime Minister David Cameron, before watching U.S. athletes on the first full day of Olympic competition. She will see more events Sunday before departing.
Other first ladies who have led recent U.S. Olympic delegations include Hillary Clinton at Lillehammer in 1994 and Laura Bush at Turin in 2006.