Washington (CNN) Defense Secretary Mark Esper said Sunday that he has "great faith in the military justice system" following President Donald Trump's interference last week in three military war crimes cases against Pentagon guidance.

"So I'd say first of all that we have a very effective military justice system, I have great faith in the military justice system, our soldiers, sailors, airmen and Marines are trained from day one about the laws of armed conflict and how to conduct themselves during wartime," Esper said in a response to a reporter's question about the President's actions on Friday.

Trump granted full pardons to Army 1st Lt. Clint Lorance and Army Major Mathew Golsteyn, and restored the rank of Navy SEAL Eddie R. Gallagher, who had been demoted. Lorance was found guilty in 2013 of second-degree murder for ordering his men to fire on three men on a motorcycle in Afghanistan. Gallagher -- who had faced a court-martial for premeditated murder and attempted murder, but was acquitted -- was demoted after being found guilty for posing for a photo with a casualty, and Golsteyn has been charged with the murder of an Afghan man in 2010. He pleaded not guilty in June.

Esper and other senior military leaders had told Trump that a presidential pardon could potentially damage the integrity of the military judicial system, the ability of military leaders to ensure good order and discipline, and the confidence of US allies and partners who host US troops.

Speaking Sunday during a joint press conference in Thailand with South Korean Defense Minister Jeong Kyeong-doo, Esper also told reporters that US service members "conduct themselves professionally in accordance with (the law) and if they don't then the United States military will take action in accordance with the (Uniform Code of Military Justice) to make sure that they are held accountable."