Amazon has finally lifted the lid on its second-annual Prime Day sale, which it's touting as the "biggest Amazon event ever."

On July 12, the online retailer will offer Prime members new deals as often as every five minutes. That compares with a new deal every 10 minutes during last year's Prime Day. In all, the sale will include more than 100,000 deals spanning "nearly all departments and categories," from televisions to vitamins.

Amazon did not provide a comparable number of items for last year's event, but said this is the largest number of deals it's offered in a single day.

The U.S. sale will kick off at 3 a.m. Eastern for existing Prime members, as well as those who sign up that day for one of its paid memberships or free 30-day trial. Unlike last year, Amazon will offer a handful deals for Prime members in the week leading up to Prime Day, on items including a 32-inch TV bundled with a Fire TV Stick, which will sell for $119.99.

"Following last year's record sales, we have dramatically increased the inventory behind many deals," said Greg Greeley, vice president of Amazon Prime.

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That includes nearly double the number of TV units in stock as compared with Black Friday and Cyber Monday combined. Last year, some shoppers complained on social media that the deals were selling out too quickly.

Amazon's Prime Day playbook is similar to its Black Friday strategy, which also rolled out deals every five minutes. Company spokeswoman Julie Law said some of the discounts will be deeper than last year's event.

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During its inaugural Prime Day sale, held last July in honor of the company's 20th anniversary, Amazon sold more units than on Black Friday 2014, which at the time was its biggest ever (Amazon's 2015 Black Friday event surpassed that metric). In addition to driving sales, the event led to more new members trying Prime than on any day in its history, Amazon said.

Though Amazon does not release information regarding the number of Prime members, Consumer Intelligence Research Partners estimates Amazon has 54 million U.S. members. The firm's data also shows that 73 percent of Amazon's 30-day trial subscribers pay for the first full year of membership. And 91 percent of first-year subscribers renew for a second year, CIRP said.

Amazon has not set an explicit goal for this year's event, though Law said the company expects it to be "another record-breaking Prime Day." She said additional details regarding specific Prime Day deals will be released closer to the event, including "far more" limited-time lightning deals and deals of the day.

Law responded to criticism that the Prime Day discounts at times seem random, saying the event is different from Black Friday in that it's not a gifting holiday. Instead, it's the time of year when shoppers are stocking up on such things as seasonal summer goods and back-to-school essentials, she said.

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"What could be weird to one person may be wonderful to someone else," Law said. "We really stand behind the deals we had last year and the deals we have this year."

Amazon's announcement, while widely expected, comes one day afterWal-Mart announced a free 30-day trial for its ShippingPass service, which is positioned as a competitor to Prime. Similar to Amazon Prime, Wal-Mart shoppers can pay an annual fee to receive unlimited two-day shipping.

Wal-Mart's version of the service costs $49 a year, compared to $99 for an annual Prime subscription. However, Prime membership includes additional benefits that aren't part of Wal-Mart's program, including unlimited streaming of movies and TV shows. Amazon also boasts a broader array of products, with more than 20 million items eligible for Prime. Walmart's U.S. site has roughly 7 million items up for grabs.