Online retail giant Inc (NASDAQ:AMZN) on Wednesday expanded its same-day delivery feature to more cities across the United States. Now, customers in Baltimore, Dallas, Indianapolis, New York, Philadelphia and Washington can avail of the service, the company said.

The Seattle-based retailer, which is trying to get more people to sign up for its Prime loyalty program, said that subscribers to the program can place their orders for $5.99 on all seven days of the week, and the products will be delivered within the day. The service has been available to customers from Los Angeles, Phoenix, San Francisco and Seattle since May. One of the company's main competitors, eBay Inc (NASDAQ:EBAY), had last month fended off rumors that it was planning to stop its same-day delivery program.

For those who do not sign up for the Prime loyalty program, will charge them a fee of $9.98 for same-day delivery for the first item and 99 cents for each additional item, according to the statement, which noted that the more than a million items on its website are eligible for the "Get It Today" program.

Amazon is also battling for space in the online grocery-delivery market, which has seen many new players enter the segment, and companies like Google and eBay are spending tens of millions of dollars to counter competition from start-up companies, as well as established players.