WASHINGTON (REUTERS) - President Barack Obama and his daughters, Sasha and Malia, went on what has become an annual book shopping spree on Saturday, stopping at a bookstore to promote an event called Small Business Saturday.

The First Family, in casual dress, stopped traffic in Politics and Prose, a tiny locally-owned store in Northwest Washington. They took time to mingle with camera-phone wielding shoppers before heading to the checkout.

They purchased about two dozen books, including The Lowland, by Jhumpa Lahiri, The Ballad of the Sad Cafe: Other stories by Carson McCullers, Red Sparrow by Jason Matthews, and The Kite Runner by Khaled Hosseini.

"It's a long list," Mr Obama said while paying, his daughters, aged 12 and 15, standing behind him. "I've got books for every age group, from 5 to 52."

Part of the American Thanksgiving tradition is shopping for holiday gifts. Big box stores have Black Friday, online retailers have Cyber Monday, and more recently, mom-and-pop stores have Small Business Saturday.

Created in 2010 by credit card company American Express , the day aims to encourage Americans to spend their holiday shopping money at locally owned businesses, which have been particularly hit hard by the economic downturn.

Last year, Americans spent approximately US$5.5 billion (S$6.9 billion) on Small Business Saturday, according American Express.

Earlier in the morning, taking a break from a game of basketball, Obama said on Twitter: "When our small businesses do well, our communities do well. Join me and visit a small business near you today to celebrate #SmallBizSat," signing with "-bo" to indicate he had authored the tweet.