Burger King Holdings Inc
Burger King, the second largest U.S. hamburger chain after McDonald's, said it would serve Seattle's Best in about 7,250 U.S. outlets by September. The new coffee drinks, with optional flavorings and whipped topping, will sell for $1 to $2.79.
Starbucks has been working to grow its Seattle's Best Coffee brand through franchisees and agreements with other restaurants such as Subway.
McDonald's McCafe coffee program, which took direct aim at Starbucks with lower-priced espresso-based drinks such as lattes and mochas, has been a hit for the fast-food giant and helped buoy sales amid a stubbornly weak economy.
High U.S. unemployment has dented breakfast sales at fast-food chains since fewer people are driving past the restaurants on their way to work.
McDonald's rolled out a breakfast Dollar Menu in January to spur morning food sales and Burger King executives said they would promote breakfast value deals in April.
Seattle's Best will replace Burger King's BK Joe brew, which was introduced in 2005.
Burger King shares rose 0.7 percent, while Starbucks gained 1 percent in afternoon trading.
(Reporting by Lisa Baertlein; editing by Andre Grenon)