Wal-Mart Stores Inc. agreed to buy e-commerce startup Jet.com Inc. for about $3.3 billion, giving the world's largest retailer the resources for a stronger shopping website to compete with market leader Amazon.com Inc.

The deal includes $3 billion in cash and $300 million in shares that will be paid over time, the world's largest retailer said Monday in a statement. Acquiring Jet.com, which achieved a $1 billion gross merchandise run rate in a little more than a year, gives Wal-Mart a website that processes an average of 25,000 orders a day and is adding 400,000 shoppers monthly.

The move is Wal-Mart's biggest attempt yet to chase down Amazon, which has dominated e-commerce in much the same way that Wal-Mart has ruled brick-and-mortar retail. Wal-Mart already had spent billions expanding its online operation, including hiring thousands of workers, opening two offices in Silicon Valley, and building large e-commerce distribution centers. It also started an annual subscription service similar to Amazon Prime, at half the price, but still trails the e-commerce behemoth in online sales.

"Wal-Mart has definitely put its stake in the ground saying, 'We're going to be winning in e-commerce,'" said Joseph Feldman, an analyst at Telsey Advisory Group. "Amazon should be concerned about what Wal-Mart is doing."

Shares of Bentonville, Arkansas-based Wal-Mart rose 0.7 percent to $74.24 at 9:06 a.m. in early trading in New York. The stock had gained 20 percent this year through the end of last week. Seattle-based Amazon was little changed at $766.66 in early trading.

Gain Sharing

Jet.com has distinguished itself in e-commerce through "gain sharing," luring buyers to add items to their orders to reduce shipping costs, and to pay with debit instead of credit cards to reduce transaction fees. Traditional store-based mass retailers such as Wal-Mart, Target Corp. and Costco Wholesale Corp. have been struggling to fend off Amazon's momentum in online shopping.