NEW YORK -- Michelle Obama is taking her "Let's Move!" campaign to Arthur Ashe Kids' Day.

The first lady will speak during Saturday's festivities, the unofficial kickoff to the U.S. Open, tennis' last Grand Slam tournament of the year. She'll join defending women's champ Serena Williams, former champions Roger Federer, Rafael Nadal and Novak Djokovic, along with celebrities including singer Ariana Grande, who has the hit song "The Way."

Mrs. Obama participated in activities at the event, held in Flushing, N.Y., in 2011.

She has been leading a national campaign to get kids more active and eating healthy meals.