More pressure on brick-and-mortar retailers? Amazon expands same-day delivery to Baltimore and Miami Inc. has expanded its same-day Prime Now delivery service to Baltimore and Miami, adding pressure to brick-and-mortar retailers and raising the bar on shipping for other online merchants.

The same-day service for Amazon Prime members made its debut in December for customers in select areas of Manhattan. Prime Now’s expansion will continue to other cities throughout the year, the Seattle-based company said in a statement Thursday.

Prime Now shoppers can get same-day delivery on tens of thousands of products, such as cereal, cleaning supplies and electronics. It is now available in select ZIP codes in Baltimore and Miami and will expand quickly, the company said. Two-hour delivery is free and one-hour delivery is available in certain areas for $7.99.

Amazon continues to add perks to its Amazon Prime membership, which costs $99 a year and includes free two-day shipping on certain items and access to Amazon’s streaming television service. The company has said that Prime has tens of millions of members and that they spend more than other Amazon shoppers.

Prime has around 40 million members, according to an estimate from Scot Wingo, the chief executive officer of ChannelAdvisor Corp., a North Carolina company that helps 3,000 merchants sell products on marketplaces including

By increasing the reach of its quick-delivery program, Amazon is stepping up competition against similar services such as Google Inc.’s Shopping Express and EBay Inc.’s Now service. The programs encourage customers to shop online for items they might otherwise buy on quick runs to nearby stores.

“Since launching, we’ve seen high demand on everything from essentials like water and paper towels to more surprising deliveries like getting a customer a hard-to-find, top-selling toy,” Dave Clark, Amazon’s senior vice president of worldwide operations, said in the statement.