US auto safety authorities said on Monday that they had ordered General Motors to recall nearly six million pickup trucks and sport utility vehicles that contain Takata airbags. The National Highway Traffic Safety Administration (NHTSA) rejected a four-year old appeal from GM and concluded the automaker "has not met its burden of establishing that the defect is inconsequential to motor vehicle safety," according to an agency statement. GM said it disagreed with the decision, but will "abide" by it "and begin taking the necessary steps." GM will recall 5.9 million vehicles in the United States and another one million vehicles overseas, a spokesman said. The recall pertains to a dozen vehicles from model years 2007-2014, including the Chevrolet Silverado, the GMC Sierra and the GMC Yukon, the NHTSA said. The agency's analysis "concluded that the GM inflators in question are at risk of the same type of explosion after long-term exposure to high heat and humidity as other recalled Takata inflators," NHTSA said. The agency gave GM 30 days to establish a schedule for notifying vehicle owners and repairing the vehicles. NHTSA has confirmed 18 fatalities in the United States due to Takata airbag explosions and another 250 cases in which people have been injured. About 63 million airbags have been recalled. jmb/cs