Amazon customers who have Prime memberships will now be able to receive more than one million items the same day they order them for no extra cost, according to CNet.

The service, announced Thursday, will be similar to the free two-day shipping offered with the $99-per-year membership. More than 20 million items can be shipped within two days.

In order to qualify for same-day shipping, customers must order at least $35 worth of merchandise per order. The same-day shipping service will be available to just 14 cities at the beginning.

Amazon has been looking forward to developing a same-day shipping service. Google and Wal-Mart would like to match them with a same-day shipping service of their own.

Prime members in select cities were able to upgrade to same-day service by adding a $5.99 charge to their order. That fee will now only be included if their total is less than $35 or if they order something that is not part of the same-day service.

Amazon is able to offer the same-day service because of its recent large investments in fulfilment centers, Chris Rupp, vice president of Amazon Prime said in an interview.

"We can get items closer to customers, get more items in stock and be able to deliver as quickly as possible," she said.

Amazon Prime customers might find the service extremely beneficial and renew their membership. New customers could also be lured into joining.

Wal-Mart plans to test out a $50-a-year unlimited free shipping service soon.

Amazon is focused on its Prime members because they spend more money than those who are not Prime members.

Amazon has already started delivering groceries to customers in select markets. In the near future, it would like to use drones to deliver orders.

The same-day delivery service will start out with availability in these cities: Atlanta, Baltimore, Boston, Dallas, Indianapolis, the Los Angeles metro area, New York, Philadelphia, Phoenix, the San Francisco Bay area, Seattle and Washington, D.C., San Diego and Tampa Bay, two cities that did not offer same-day service in the past.

Amazon same-day service will be available seven days a week. For more information and to see which zip codes qualify, visit Amazon.com/sameday.