Joint Chiefs of Staff Chairman Gen. Mark Milley says he regrets his participation in President Trump’s photo opportunity outside St. John’s Church last week.

“I should not have been there,” Milley said during a recorded message aired at the graduation of the National Defense University on Thursday morning. “My presence in that moment and in that environment created a perception of the military involved in domestic politics.”

“As a commissioned, uniformed officer, it was a mistake that I have learned from,” he said. “And I sincerely hope we all can learn from it.”

Milley was photographed in combat fatigues walking with Trump to the historic church last Monday, shortly after demonstrators protesting the police killing of George Floyd were forcibly cleared from Lafayette Square by federal law enforcement and National Guardsmen.

Trump has been widely criticized for the photo-op — including by his former Defense secretary, James Mattis — and his administration has withstood scrutiny for the decision to clear the protesters.

Milley acknowledged in his prerecorded remarks Thursday that the incident triggered a national conversation about the role of the U.S. military in civil society. He went on to emphasize the importance of preserving the principle of a military that is not involved in politics.

“We who wear the cloth of our nation come from the people of our nation and we must hold dear the principle of an apolitical military that is so deeply rooted in the essence of our republic,” Milley said in the taped address.

He spoke at length about Floyd’s "senseless and brutal killing" and racial injustice in general, expressing support for peaceful protesters and underscoring the work ahead for the United States to address racism.

"[Floyd’s] death amplified the pain, the frustration and the fear that so many of our fellow Americans live with day in, day out," Milley said.

It’s unclear how Milley’s remarks will be received at the White House. The White House and other administration officials, including Attorney General William Barr, have defended the events in Lafayette Square, insisting the clearing of protesters was warranted and not connected to Trump’s decision to visit St. John’s.

Defense Secretary Mark Esper told reporters during a news conference last week that he was aware of Trump’s destination when he accompanied him to the church, which had been vandalized the night prior during violent protests, but that he didn’t know it would be a photo opportunity.

“I did know that following the president's remarks on Monday evening that many of us were wanting to join President Trump and review the damage in Lafayette Park and at St John's Episcopal Church,” Esper said. “What I was not aware of was exactly where we were going when we arrived at the church and what the plans were once we got there.”

Esper also broke with Trump by saying he would not support the use of the Insurrection Act to allow the deployment of active-duty troops to quell domestic protests after Trump threatened to do so in order to crack down on looting and rioting.

Esper’s statement caught the White House by surprise, and Trump reportedly wanted to fire the Cabinet member over the disagreement but was talked out of it.

The events last week prompted a cascade of criticism from former military officials, including Mattis, who has otherwise been resistant to offering direct criticism of the president since he resigned in December 2018.

“When I joined the military, some 50 years ago, I swore an oath to support and defend the Constitution,” Mattis wrote last Wednesday in a statement published by The Atlantic. “Never did I dream that troops taking that same oath would be ordered under any circumstance to violate the Constitutional rights of their fellow citizens — much less to provide a bizarre photo op for the elected commander-in-chief, with military leadership standing alongside."

Trump has since criticized Mattis on Twitter, calling him the  “world’s most overrated general” and suggesting he was ineffective at his job. 

Updated at 11:55 a.m.