Burger King Corp. is weighing the addition of a delivery option to its restaurants in the United States, a convenience the chain has long offered in several countries overseas. Four restaurants in the Washington, D.C., area currently are testing delivery service, said Kristen Hauser, a spokeswoman for the Miami-based quick-service chain. The test will be expanded to 16 stores by Jan. 23, she said, but no specifics regarding the timing of a possible national roll out were available. Burger King said it has been offering delivery for years with great success at locations in Mexico, Turkey, Brazil, Columbia and Peru. For the U.S. test, guests can order online at www.bkdelivers.com or by phone. The restaurants will deliver to a physical address within a 10-minute drive of test units. Guests are charged a $2 fee for delivery and the minimum order is $8 to $10, depending on the store. The delivery menu includes items like burger combo meals, chicken tenders and bottled drinks. But the chain is not delivering fountain drinks, ICEE beverages, shakes, coffee or breakfast items, Hauser said. The test stores are using new delivery packaging technology in conjunction with thermal bags to keep food hot and fresh, Hauser said, although no details were available. If the company decides to expand the service nationally, Burger King could become the first national quick-service burger chain to do so. McDonald’s for some time has offered delivery service in select stores in Manhattan, but spokeswoman Danya Proud said the company has no immediate plans to expand the option. Johnny Rockets has tested bicycle delivery in some cities, as have other limited-service brands, like Subway, Pinkberry and Wow Bao. Burger King, which operates or franchises about 12,400 locations globally, has been exploring a number of innovations since it was acquired by private investor group 3G Capital Management in 2010. In December, the company said it plans to expand use of the new Coca-Cola Freestyle beverage machines to more than 850 company-owned locations. Earlier, the chain rolled out new French fries as part of an ongoing menu upgrade. Other additions have included new soft-serve ice cream and desserts, and the premium Chef’s Choice burger.