President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE reportedly oversaw a heated meeting on immigration Monday that split some of his top advisers over his decision to authorize troops at the border to use lethal force against migrants.

Several White House aides and advisers who support the president’s hard-line views on immigration clashed with White House chief of staff John Kelly John Francis KellyMORE and Homeland Security Secretary Kirstjen Nielsen Kirstjen Michele NielsenMore than million in DHS contracts awarded to firm of acting secretary's wife: report DHS IG won't investigate after watchdog said Wolf, Cuccinelli appointments violated law Appeals court sides with Trump over drawdown of immigrant protections MORE, who opposed the order, according to Politico.

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The White House did not immediately respond to a request for comment from The Hill.

According to Politico, those that clashed with Kelly and Nielsen were senior policy adviser Stephen Miller; Chris Crane, president of the National Immigration and Customs Enforcement Council; and Brandon Judd, president of the border patrol union. All of them argued the order fell within the president’s constitutional powers.

Kelly and Nielsen eventually conceded, and Kelly signed a Cabinet order Wednesday allowing some troops to engage in law enforcement activities and use lethal force, Politico reported.

"While a range of issues were discussed on a Monday call, the cabinet memo was not one of those topics. In reality, I have been clear: our agents and officers must have the ability to protect themselves, and to be protected by others, if they face critical situations on the border," Nielsen said in a statement to Politico.

Troops may “perform those military protective activities that the Secretary of Defense determines are reasonably necessary,” according to the report, which explains that “protective activities" include “a show or use of force (including lethal force, where necessary), crowd control, temporary detention, and cursory search.”

The order appeared to catch the Pentagon by surprise, with Secretary of Defense James Mattis James Norman MattisBiden courts veterans amid fallout from Trump military controversies Trump says he wanted to take out Syria's Assad but Mattis opposed it Gary Cohn: 'I haven't made up my mind' on vote for president in November MORE telling reporters Wednesday, “I’m reviewing that now.”

“The brave men and women at Customs and Border Protection willingly put themselves in extremely dangerous situations every day to protect Americans and their families,” deputy White House press secretary Hogan Gidley told Politico. “The President’s authorization ensures the Department of Defense can step in to protect those who protect us.”

Trump confirmed Thursday that troops he sent to the southern border had authorization to use such force.

“If they have to, they’re going to use lethal force. I’ve — I’ve given the okay. If they have to. I hope they don’t have to,” he said.

News of the meeting comes amid speculation that Kelly and Nielsen will be swept up in an administration-wide staff shake-up. Trump has only aired grievances against the two, particularly regarding their stances on immigration.

Trump has staked particularly hard-line positions on immigration as a group of thousands of Central American migrants make their way to the southern border to seek asylum. The president has attempted to limit their pathways to asylum and threatened to close the entire border to prevent what he says are gang members from entering the country.

“Our military is being mobilized at the Southern Border. Many more troops coming. We will NOT let these Caravans, which are also made up of some very bad thugs and gang members, into the U.S. Our Border is sacred, must come in legally. TURN AROUND!” he tweeted last month.