Walmart© Provided by Business Insider Walmart

Walmart is expanding its grocery delivery service across the US this year, the company announced Wednesday.

The service, which offers same-day delivery in as little as three hours, will be expanded from six metro areas to more than 100, ultimately reaching more than 40% of US households by the end of the year.

Walmart will charge a flat fee of $9.95 for delivery and require a minimum order of $30 to access the service.

The retailer plans to use its own personal shoppers to pick and pack delivery orders in more than 800 stores. It will partner with Uber and other crowdsourced delivery companies to transport the groceries to customers’ doorsteps.

“We’re moving fast to save our customers time,” Tom Ward, vice president of digital operations for Walmart, said on a call with reporters on Tuesday.

Walmart© Provided by Business Insider WalmartHe said Walmart will be “aggressive” with the rollout and plans to eventually make the service available to all of its US shoppers.

Walmart is going all-in on grocery delivery one month after Amazonannounced it would start offering members of its Prime service free two-hour delivery from Whole Foods, which Amazon acquired last year in a $13.7 billion deal.

Target and Kroger have also been expanding their grocery delivery services. Target announced earlier this year that it plans to offer same-day delivery of groceries from half of its 1,800 stores using Shipt, a delivery startup it recently acquired.

Meanwhile, Kroger said Monday that it’s expanding its delivery services to 500 additional stores — from the nearly 900 stores where it’s currently offered — through its partnership with Instacart.

Ward declined to directly address rival delivery services. But he made a veiled reference to Instacart, which sometimes charges customers higher prices on goods than the retailers that sell them.

“Unlike other services, customers will find the same everyday low prices” on groceries through Walmart’s website and app, he said.