Amazon is ramping up its speedy delivery service by offering one-hour and three-hour shipping in markets across the US, including Los Angeles and Chicago, in its latest efforts to stave off e-commerce competition from its biggest rival Walmart.

Fast delivery has been a significant part of Amazon’s push to increase basket sizes and shopping frequency. The company in December announced a separate service called “Amazon Now” to deliver grocery items and everyday essentials in 30 minutes or less in select locations, including Seattle and Philadelphia.

“We saw an opportunity to use our unique operational expertise and delivery network to help make customers’ lives a little easier while unlocking even more value for Prime members,” Amazon senior vice president of Worldwide Operations Udit Madan said in a press release.

The Seattle-based e-commerce giant said on Tuesday that its one-hour delivery option is available on more than 90,000 products, including everyday essentials, toys and toilet paper, and will rely on its existing same-day delivery network. The 60-minute option has launched in major US metropolitan areas and smaller cities like Boise, Idaho. The three-hour option has launched in more than 2000 cities and towns. Perishable groceries are available in select areas, Amazon said.

To ensure the one-hour and three-hour orders are fulfilled in a shorter amount of time, Amazon introduced designated work stations for these orders within existing same-day delivery centers, new yellow labels that are placed on the packages for easy identification and updated signage throughout the site to easily direct delivery partners, the company said.

Using the high-speed delivery comes at an extra fee. Prime members pay an extra $9.99 for one-hour delivery and $4.99 for three-hour delivery. Shoppers without Prime memberships pay $19.99 for one-hour orders and $14.99 for three-hour deliveries.

• Reporting by Arriana McLymore in New York City; Editing by Stephen Coates, of Reuters.