Amazon.com's annual Prime Day sales event is scheduled for July 8 through July 11, expanding to four days from two days compared to last year, the company announced Tuesday.

"We're extending it to four days because our members have told us they just need more time to shop the deals," Jamil Ghani, Amazon vice president of worldwide prime, told Reuters.

Amazon's expanding Prime Day comes as U.S. shoppers and retailers face uncertainty on how tariffs will impact prices and product availability, said Rob Garf, senior vice president of strategy and insights at retail marketing firm Cordial.

U.S. shoppers spent $14.2 billion, up 11% year-over-year, during Amazon's July 2024 Prime Day event, according to Adobe Analytics. The e-commerce giant often faces competing sales events from Walmart, Target and, now, ByteDance's TikTok Shop, which are trying to lure shoppers into spending early on back-to-school and back-to-college merchandise including personal electronics, apparel and home goods.

The online retailer wants to entice younger shoppers to sign up for its subscription service Prime, by offering discounted memberships for people between the ages of 18 and 24 and other perks. Prime subscriptions typically cost $14.99 per month or $139 per year.