Amazon.com Inc. announced Tuesday that its Prime Day sales event will run 48 hours this year, starting at midnight Pacific time on July 15. That’s 12 hours longer than the 36 hours the sale ran last year.

The sale will be available to consumers in 18 countries, including the United States, United Kingdom, Germany, France, China and Australia. That’s one more than last year thanks to the addition of United Arab Emirates.

Amazon created Prime Day in 2015 to celebrate Amazon’s 20^th year in business. While the initial event was 24 hours, Amazon has expanded its length each of the past three years. The sale ran 30 hours in 2017 and 36 hours last year.

Over the past four years it has cemented its place as a key summer sales event that generates additional business for Amazon—and the retailer’s marketplace sellers—before the holiday shopping season, while also spurring other retailers to latch on to the event with their own counter sales. For example, last year eBay Inc., Target Corp. and Walmart Inc. were among the competitors offering steep discounts on, or around, Prime Day. And within hours of Amazon’s announcement, Target rolled out a July 15 and 16 counter sale, Target Deal Days, which it bills as its “biggest sale of the summer,” noting there’s “no membership required to shop thousands of deals.”

Prime Day is also a vehicle for Amazon to drive shoppers to sign up for its Prime membership, a $119 per-year loyalty program that offers such perks as free one- or two-day shipping, digital photo storage and video streaming. The Prime Day deals are only available to Prime members.

“Our vision is that Prime Day should be the absolute best time to be a member–when you can enjoy shopping, savings, entertainment and some of the best deals Prime members have ever seen,” says Jeff Wilke, Amazon CEO worldwide consumer.

Prime Day last year was the second-biggest sales day for Amazon, after Cyber Monday 2018, the company said in November. Amazon doesn’t disclose its Prime Day sales figures, but Internet Retailer estimates sales hit $4.19 billion globally during the 36-hour sales event July 16–17, 2018. That was up nearly 74% from $2.41 billion during the 2017 Prime Day (a 30-hour sales event July 11–12, 2017), according to Internet Retailer estimates.

This year’s longer sale will likely help Amazon drive even more growth, says Charlie O’Shea, a retail analyst at Moody’s. “Amazon’s announcement that its annual Prime Day promotion now requires ‘pluralizing’ as it will be two days this year will make an already acutely-competitive retail environment even tougher,” he says. “This is yet another example of the flexibility Amazon has to push the pricing envelope, in this case to broaden and deepen the benefits to Prime members, which creates a conundrum for all retailers, with the smaller, financially weaker retailers the most at risk. Making this even tougher, Walmart and Target will react, further turning up the competitive heat.”

This year’s sale will feature more than 1 million discounts, Amazon says, including a number of limited-time offers and exclusive launches online and in Amazon’s physical stores, such as Amazon Books and Whole Foods Market. To promote the sale, Amazon on Tuesday rolled out what it bills as a $120 discount on a Toshiba HD 43-inch Fire TV edition smart TV that will run through June 30. It is also discounting its Garage myQ Smart Garage Hub + Amazon Cloud Cam (Key Edition) Kit, which is an internet-connected garage door system. Amazon also plans to launch a Prime Day page that’s dedicated to Amazon Handmade, its Etsy-like marketplace.

Those efforts position Amazon to generate even greater sales than it generated last year.

Amazon is No. 1 in the Internet Retailer 2019 Top 1000. Walmart is No. 3 and Target is No. 16.