Best Buy is growing its same-day delivery in its fight against Amazon

Best Buy is expanding its same-day delivery service to ward off aggressive competitors.

Starting on September 6, the electronics retailer will offer same-day shipping in 27 cities in the US. That's double the number of cities available previously and includes San Diego, Denver, Austin, and Tampa. By the end of the year, the company expects the service will expand to 40 cities.

Best Buy is also reducing the price of the same-day delivery service from $14.99 to $5.99 per order, as well as expanding the list of products eligible for the service.

One of two third-party contractor couriers will make the delivery on behalf of the retailer.

With the new service, customers who place their orders on BestBuy.com and elect for same-day shipping by 3 p.m. (2 p.m. on Sundays) will receive their packages by 9 p.m. that day.

"We have always wanted to help our customers get their purchases from Best Buy how and when they want them," said Allison Peterson, president of BestBuy.com, said in a statement. "Our stores have always been an option, but we know that there are times when a customer wants their items delivered to them quickly. We're happy that by the holidays, many more customers will be able to choose same-day delivery and have it be an option on more items than ever before."

Best Buy, like many retailers, is aggressively stepping up its online ordering business in the wake of stiff competition from Amazon. The e-commerce giant's Prime Now service, for example, offers delivery in a matter of hours.

According to the Wall Street Journal, who cited data from Traqline, Best Buy is still the largest electronics retailer by sales in the US, with a 29.3% share.