Starbucks Corp will roll out its biggest drink size yet -- the 31-ounce Trenta -- in all of its U.S. coffee shops by May 3, the company said on Sunday

The new size will be available only for iced coffee, iced tea and iced tea lemonade drinks in the United States. The Trenta is 7 ounces larger than Starbucks' Venti cup for iced drinks, which currently is its largest size on offer.

Drinks in the Trenta size will cost 50 cents more than similar Venti-sized iced drinks, the company said.

Seattle-based Starbucks tested the new size in several U.S. markets last year, saying it was responding to customer demand for larger cold beverages.

The Trenta size will debut in 14 states, including Virginia, Georgia, Florida, Texas, Hawaii and Arizona, on January 18 and in California on February 1.

The world's biggest coffee chain said unsweetened drinks in the new size will have fewer than 90 calories and that sweetened versions will have less than 230 calories.

McDonald's Corp, the world's biggest fast-food restaurant chain, has taken direct aim at Starbucks with frappes, fruit smoothies and espresso drinks such as lattes and cappuccino. It also has lured customers by selling 32-ounce (946.4 ml) sweet tea drinks for $1 each.

U.S. convenience stores, which have been taking on restaurant chains with an expanded selection of low-cost, quick-serve fare, for years have sold fountain drinks in large sizes, including 32 ounces and 64 ounces (1.9 L).

(1 U.S. fluid ounce = 29.57 milliliters)

(Reporting by Lisa Baertlein; Editing by Richard Chang)

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