A former Army Special Forces officer is accusing retired Marine General James Mattis, President-elect Donald Trump's pick to be defense secretary, of "leaving my men to die" after they were hit by friendly fire in Afghanistan in 2001, NBC News reported.

Mattis has not commented publicly on the incident, which was chronicled in a 2011 New York Times bestselling book, "The Only Thing Worthy Dying For," by Eric Blehm, which portrays Mattis as stubbornly unwilling to help the Green Berets.

His actions, which were not formally investigated at the time, are now likely to get far more scrutiny during the retired general's Senate confirmation process.

Trump's transition team did not respond to request for comment from NBC News.

Mattis, whose 2013 retirement from the military means he would need a waiver from Congress to serve as the civilian Pentagon chief, did not respond to a request for comment from NBC News.

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