Amazon (AMZN) is offering free same-day shipping for its Prime subscribers in some of its key markets. The e-commerce giant said the service will be available without a fee for a limited time, and added that it is expanding same-day delivery to two additional cities. The online retailer's quick shipping service previously cost $5.99 for same-day delivery, with a $99 annual Prime membership. But now, the service is free for its Prime customers with an order of more than $35. Amazon Prime members will need to place their order by noon to receive the package delivery by 9 p.m. on that same day. The Seattle-based e-commerce giant also announced that it is expanding the same-day delivery service to a total of 14 cities, with the addition of San Diego, California and Tampa Bay, Florida. TheStreet's Kurumi Fukushima reports in New York.