AUSTIN, Texas — Whole Foods says its sales at established locations slipped in its fiscal first quarter and forecast the figure to be flat to down 2 percent for the year, as it works to keep prices down and fend off rivals.

The Austin, Texas, company noted that its comparable store sales have been “particularly difficult to predict” given the competitive environment. Whole Foods has been under pressure as organic foods and products marketed as natural have become increasingly mainstream, with big-box retailers devoting more space to such items.

That has prompted Whole Foods to try and appeal to a broader customer base by keeping prices down. On Wednesday, it announced the launch of its digital coupons on its mobile app.

For the three months ended Jan. 17, the company said sales fell at 1.8 percent at stores open at least 57 weeks. The figure is a key metric of economic health.

Whole Foods, which has more than 430 stores in the U.S., Canada and the United Kingdom, including one in Maine, says it still sees potential for 1,200 locations in just the U.S. A newer branch of “365” stores it is opening that focuses more heavily on value can expand on that footprint, the company says.