NEW YORK (AP) — Walmart is buying fast-growing online retailer Jet.com for $3 billion in cash plus $300 million in stock, scooping up a newcomer that launched a year ago with the intention of challenging online leader Amazon.

The hefty price underscores how Walmart is trying to compete more aggressively and effectively for younger and more affluent customers as it has seen its online business growth slow, even with big investments in distribution centers and expanding services.

As part of the deal, Jet. com co-founder and CEO Marc Lore will oversee both that site and walmart.com, and will report to Walmart Stores Inc. Chief Executive Doug McMillon. Lore brings to the role a rich e-commerce resume as founder of Quidsi, the parent of Diapers.com, which was bought by Amazon for $500 million in 2010.

Analysts say the acquisition still won’t enable Walmart to catch up to Amazon in sales, but it will help narrow that gap and should widen the distance between Walmart and other online retailers.

The deal also reflects the difficulties for startups like Jet.com of making it on their own in a sphere Amazon dominates with its network of distribution hubs and the powerful asset of its Prime membership program.

The move follows a series of acquisitions by major traditional retailers of online startups, with Hudson’s Bay, which owns Saks Fifth Avenue, purchasing flash-sales site Gilt Group and Bed, Bath & Beyond buying One Kings Lane.