WASHINGTON, Sept 30 (Reuters) - General Motors Co (GM.N)and Ford Motor Co (F.N) said Thursday they will cut additional production because of the nagging semiconductor shortage that has hit global auto production. GM, the largest U.S. automaker, said it will extend by two weeks a halt to Chevrolet Blazer sport utility vehicle production at its Ramos plant in Mexico because of the ongoing chips shortage as it resumes production at other North American plants. GM said production will resume Monday at its Lansing Grand River Assembly plant that builds the Chevrolet Camaro and the Cadillac CT4 and CT5. Cadillac production has been halted at the Michigan plant since May. Production of the Blazer at the Ramos plant, which has been halted since Aug. 23, will now not resume before Oct. 15. Ford said next week it will halt production at its Flat Rock Assembly Plant where it builds the Mustang. Ford will halt production of the Transit next week at its Kansas City Assembly Plant but it will continue to build F-150 trucks. Ford"s Kentucky Truck Plant next week will operate on one shift rather than the three normal shifts. Reporting by David Shepardson, Ben Klayman and David Gregorio Our Standards: The Thomson Reuters Trust Principles.