By Nathaniel Meyersoh, CNN Business

(CNN) -- For the first time, Amazon is offering free shipping on all holiday orders in an effort to add new Prime members and juice the season's sales numbers.

Last year, Amazon shoppers without Prime memberships had to spend at least $25 to earn free shipping, but Amazon is waiving the purchase minimum starting Monday to give "customers even more convenient and faster delivery options," the company announced.

The National Retail Foundation forecasts holiday retail sales will climb by up to 4.8% compared to a year ago.

Amazon's plan could overshadow holiday strategies from top competitors like Target, which offers free two-day shipping on all orders from November 1 to December 22.

The promotion will make hundreds of millions of items eligible for free shipping, Amazon said. By comparison, Walmart, one of Amazon's fiercest competitors sells around 75 million products online.

Amazon needs to pump up sales after the company's revenue projection for the remainder of the year fell below some Wall Street analysts' estimates. The company expects sales for the fourth quarter to be between $66.5 billion and $72.5 billion.

Amazon did not announce a cutoff date for the promotion, but said that free shipping will be available for all orders arriving in time for Christmas. The company usually sets the final date toward the end of the season.

Prime members already get free shipping on all eligible orders with no minimum required, but without the holiday promotion, non-Prime shoppers must spend at least $25 to land free shipping.

Prime members in the United States do get a holiday perk, however. Amazon is making more than three million items eligible for same-day delivery for the holidays.

In recent months, Amazon has extended same-day delivery from Whole Foods through Prime Now to more than 60 cities.