White House senior adviser Stephen Miller Stephen MillerSpecial counsel investigating DeVos for potential Hatch Act violation: report Trump confirms another White House staffer tested positive for COVID-19 Biden pick creates furor, underscoring bitterness over Obama immigration policy MORE’s attempt to engineer a second shake-up at the Department of Homeland Security (DHS) was blocked this week by acting Secretary Kevin McAleenan, who later threatened to resign unless he was given more control over the agency.

Administration officials told The Washington Post that the closed-door clash revolved around Mark Morgan, a former FBI agent who is 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’s pick to be the new director of U.S. Immigration and Customs Enforcement (ICE).

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Miller Wednesday reportedly urged the president to put Morgan atop U.S. Customs and Border Protection (CBP) instead.

McAleenan told acting White House chief of staff Mick Mulvaney Mick MulvaneyOn The Money: House panel pulls Powell into partisan battles | New York considers hiking taxes on the rich | Treasury: Trump's payroll tax deferral won't hurt Social Security Blockchain trade group names Mick Mulvaney to board Mick Mulvaney to start hedge fund MORE and others the next day that he was in charge of the department and would make or should at least be involved in DHS personnel decisions.

The DHS acting secretary prevailed and ensured Morgan will take his role atop ICE as planned. Matthew Albence, the current acting director whom Miller wanted to lead ICE, will return to his job as deputy director.

“This was a power struggle between McAleenan and Miller, and McAleenan won,” one senior official with knowledge of the situation told the Post.

The White House told the Post that McAleenan and Miller have since resolved some of their differences.

The White House and DHS did not immediately respond to requests for comment from The Hill.

An escalating immigration crisis has put increased pressure on Trump to make good on his campaign promise to tackle ongoing issues at the border and ramp up scrutiny of DHS efforts to curtail the flow of migrants in the U.S.

Miller engineered a shake-up at DHS last month that led to the ouster of 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 and the previous acting ICE director, Ronald Vitiello, among others. Miller, a well-known immigration hawk, reportedly urged Trump to form a team that will more aggressively execute his policies at the border.

Nielsen and Vitiello before the shake-up had reportedly challenged a plan by Miller to carry out mass arrests of women and children eligible for deportation in 10 cities.

Officials told the Post that Miller told colleagues he would support McAleenan following his nomination.