(Bloomberg)—Starbucks Corp. will expand its mobile-ordering service to four Western states, building on a test that lets customers in Portland, Oregon, transmit their requests for lattes and mochas before entering a store.

Starbucks will bring its mobile order and pay program to 650 cafes across Oregon, Washington, Alaska and Idaho beginning March 17, the company said in a statement Tuesday. While Starbucks’ app already lets customers nationwide pay on-site for their coffees, the ability to order ahead of time only started being tested in December at 150 stores in the Portland area.

CEO Howard Schultz said earlier this year that 16% of Starbucks’ U.S. store transactions now come through its mobile-payment app, which was introduced in 2009. The app has more than 13 million users, who pay and earn reward points by having their phones scanned at the register.

Starbucks, based in Seattle, will roll out mobile ordering nationwide this year, with plans to offer delivery in select markets in the second half of 2015. Schultz has referred to the plan, part of Starbucks’ strategy to keep U.S. sales growing, as “e-commerce on steroids.”

Kevin Johnson, a former Juniper Networks Inc. executive, was chosen in January to replace Troy Alstead as chief operating officer at Starbucks, underscoring the vital role technology plays at the company.

The stores in Portland have allowed iPhone users to order using the Starbucks app before they arrive. Starbucks plans to add the features to its Android app this year, according a spokeswoman for the company.