WASHINGTON (AP) -- First lady Michelle Obama says she's excited about leading the U.S. delegation to the London Olympics this week but remains "heartbroken" by the Colorado movie theater shooting.

In a conference call with reporters, she said Americans have "come together as one family" over the shooting. And though she says the trip starting Thursday is a "dream come true," she's remembering the people of Aurora, Colo., in her prayers.

While in London, Mrs. Obama will have breakfast with the U.S. Olympic team and attend a reception at Buckingham Palace. She'll also host a "Let's Move!" event with American and British children and the children of U.S. troops as part of her campaign against childhood obesity. She says she want to "turn the spirit of the games into action."