Starbucks Corp (SBUX.O) and Danone SA (DANO.PA) on Tuesday will begin selling a smoothie line at more than 4,300 U.S. Starbucks shops as part of a Greek yogurt partnership that will also include yogurt parfaits and ready-to-eat yogurt to be sold by grocers.

The rollout comes as Starbucks seeks to double food sales and as Danone's popular Dannon yogurt brand wrestles with Chobani in the popular Greek yogurt category. The partners each declined to give sales estimates.

The coffee chain, which has about 12,000 U.S. shops, will offer smoothies made with its own Evolution Fresh juices and an exclusive-to-Starbucks Dannon Greek yogurt at shops in Washington state, Oregon, Alaska, Northern California and Idaho.

Priced at $5.95 for a 16-ounce size, the smoothies will come in three flavors and can be customized by adding ingredients such as protein powder and fresh kale, said Jeff Hansberry, president of Starbucks' Evolution Fresh brand.

In early May, Starbucks and Dannon will begin selling Evolution Fresh Greek yogurt parfaits in about half of Starbucks' U.S. stores.

Then, this summer, the partners will start selling fruit-on-the-bottom Greek yogurt cups at U.S. supermarkets.

Evolution Fresh Greek yogurt is a proprietary blend for Starbucks that includes three yogurt cultures, instead of the traditional two, said Jeffrey Rothman, vice president of marketing for Dannon. Rothman added that it is the mildest, creamiest Greek yogurt Dannon makes.

U.S. yogurt sales totaled $8.3 billion in 2014 and were dominated by Dannon, according to research firm Euromonitor International, which does not break out sales in popular Greek yogurt category.