The United Auto Workers union on Tuesday threatened a strike in five days at a key plant making the company’s most important model, the F-150 pickup truck, due to disagreements on a new “local” labor contract, the UAW’s Ford chief said. UAW Vice President Jimmy Settles said a strike authorization had been approved by UAW President Dennis Williams. Ford is currently in talks for a new four-year national contract affecting Ford’s 52,700 U.S. unionized workers as well as for a new pact for the 7,500 workers at the Kansas City Assembly Plant in Missouri.