PURCHASE, N.Y. – PepsiCo announced this week that it will roll-out its new mid-calorie soda, Pepsi True, in mid-October. But don’t expect to get it in stock at your convenience store — the company will be launching the new stevia-sweetened drink exclusively on Amazon.com, with eventual rollout to brick-and-mortar retailers.

Pepsi True is made with sugar and stevia, containing about 30% fewer calories than regular Pepsi. Just as importantly, it contains no high-fructose corn syrup and no artificial sweeteners, two ingredients that have become increasingly controversial in recent years. Amazon will sell the soda in 24-packs of 7.5-ounce cans.

At the same time, Coca-Cola has begun testing its mid-calorie cola, Coca-Cola Life, in stores in the Southern United States before a planned national rollout next month.

Carbonated soft drink sales have been declining for almost a decade, and more recently diet soft drink sales have begun to decline at an even faster rate than regular, sugared soft drinks. Now, manufacturers are hoping the mid-calorie soda — lower calories without the chemicals — may provide a much-needed boost to the industry. A 7.5-ounce can of Pepsi True, for example, contains 60 calories. That compares with 100 calories for the identical-size can of regular Pepsi. Similarly, the 8-ounce glass bottle of Coca-Cola Life, now sold in Fresh Market locations in a handful of Southern states, is 60 calories.

Last month, in another e-commerce link with Amazon, Coca-Cola brought back the highly caffeinated citrus soda, Surge, also initially sold only online via Amazon.