WASHINGTON — General Motors must recall 5.9 million vehicles with Takata airbag inflators after a U.S. safety agency said Monday it had rejected the automaker’s petition to avoid the callback.

The National Highway Traffic Safety Administration said GM must recall the 2007-2014 trucks and SUVs because the inflators “are at risk of the same type of explosion after long-term exposure to high heat and humidity as other recalled Takata inflators.” GM has it could cost it $1.2 billion if it were required to replace airbag inflators it had sought to avoid fixing.

The recall will cover about 7 million vehicles globally, GM said, including 544,000 units in Canada.

GM said it would comply with the order.

“Although we believe a recall of these vehicles is not warranted based on the factual and scientific record, NHTSA has directed that we replace the airbag inflators in the vehicles in question,” GM said in a statement. “Based on data generated through independent scientific evaluation conducted over several years, we disagree with NHTSA’s position.  However, we will abide by NHTSA’s decision and begin taking the necessary steps.”

The defect, which leads in rare instances to airbag inflators rupturing and sending potentially deadly metal fragments flying, prompted the largest automotive recall in U.S. history of about 63 million inflators. Worldwide, about 100 million inflators by 19 major automakers were recalled.

The recall includes some Cadillac Escalade, Chevrolet Silverado, Chevrolet Suburban, Chevrolet Tahoe, GMC Sierra and GMC Yukon vehicles built over an eight-year period.

In total, 18 U.S. deaths have been reported tied to Takata airbag inflators — though none in GM vehicles.

To date, 15 U.S. deaths have been reported in Honda vehicles, two in Ford Motor Co. vehicles and one in a BMW since 2009.

GM first filed a petition in 2016 seeking to avoid the recall. NHTSA noted that in nearly 30 years, it has only granted one petition deeming a “defect is inconsequential to motor vehicle safety” and “in a vastly different set of circumstances.”

GM argues the 5.9 million vehicles are different from other vehicles with Takata inflators. The automaker estimates that 66,894 Takata passenger airbag inflators have deployed in the vehicles under review without a reported rupture.

Peter Prieto, a lawyer representing consumers in Takata lawsuits, said the decision “proves that GM’s Takata inflators are neither unique nor special. GM’s inflators carry the same risk of exploding and severely harming vehicle occupants as all other Takata inflators.”