Pressure increased on Firestone and Ford Motor Co. on Thursday as Congress called for a closer look at the company's recall of an estimated 6.5 million tires and Firestone's hourly workers moved closer to a strike. A Senate panel will call top officials at Firestone, Ford, and the National Highway Traffic Safety Administration (NHTSA) to testify about the tires, a congressional aide said. A U.S. House panel said it will send investigators to Ford's Dearborn, Mich., headquarters on Friday to discuss the recall with executives.