US Citizenship and Immigration Services Director L. Francis Cissna is leaving the agency in the wake of a major shakeup in the last month among the leadership at the Department of Homeland Security, according to an email sent to agency employees Friday evening.

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(CNN) — US Citizenship and Immigration Services Director L. Francis Cissna is leaving the agency in the wake of a major shakeup in the last month among the leadership at the Department of Homeland Security, according to an email sent to agency employees Friday evening.

“At the request of the President, I submitted my resignation today effective June 1, 2019,” he wrote.

USCIS spokesman Dan Hetlage confirmed Cissna’s resignation.

President Donald Trump is expected to tap former Virginia Attorney General Ken Cuccinelli to be the next director of USCIS, but it has not yet been formally announced, according to a senior administration official.

Earlier this week, CNN reported that Cuccinelli was expected to take a top job at the Department of Homeland Security to help steer the administration’s immigration policies, another senior administration official said.

Cissna’s departure is the latest in a string of top officials in the Department of Homeland Security to either be moved from their positions or forced to leave the department. The vacancy will leave all three major federal immigration agencies without permanent leaders.

“As an immigration law and policy professional dedicated to the rule of law like so many of you, I appreciate that this opportunity to serve was a unique experience,” wrote Cissna in an email thanking the workforce and reflecting on his 20 months leading the agency.

CNN reported last month that amid the DHS shakeup, there were rumors that Cissna could possibly be pushed out of the administration.

USCIS is responsible for administering and adjudicating legal immigration benefits.

Cissna, who led the agency since October 2017, was seen by immigration advocates as executing a hardline policy agenda that was aimed at restricting the US legal immigration system. But he also had his disagreements with the White House over policy implementation.

The relationship between the White House and Cissna, who volunteered for the Trump campaign, appeared to have taken a turn for the worse sometime last fall.

There has been “growing frustration” in the administration that USCIS was “not moving fast enough, going far enough” with the authorities it has, according to an administration official.

Last fall, Cissna got in a shouting match on a conference call with a senior White House official, who was urging Cissna to take a stronger stance on illegal immigration and asylum reform, according to a source familiar with the situation.

But last month, a USCIS official sought to tamp down reports of any tension with the White House.

“USCIS Director Cissna is relentlessly focused on advancing President Trump’s agenda forward to the maximum extent permitted under the law and to say otherwise is false,” said a USCIS official in a statement.

Cissna has said his priorities at USCIS were promoting security, “faithfully” administering the nation’s immigration laws and “moving the agency into an electronic world.”

“I want to bring USCIS into the 1990s,” he joked at the Immigration Law and Policy Conference last year.

However, he faced backlash from advocates and lawmakers on a number of steps the agency took, including changing its mission statement, moving to close its international offices and the proposed “public charge” rule.

Amid the rumors of this ouster last month, Cissna’s supporters came to his defense.

Republican Sen. Chuck Grassley urged the White House both publicly and privately not to fire Cissna, who previously worked for the Iowa senator when Grassley chaired the Judiciary Committee. “I spoke about the competence of people I know,” Grassley said of his message to White House officials.

“It would be a huge mistake for the administration to get rid of Director Cissna,” said Rosemary Jenks, director of government relations at NumbersUSA, a group that supports reduced immigration last month.

“There’s no one more knowledgeable of the inner workings of USCIS than Cissna.” She added that Cissna “excels” at working within the framework of the law.

Mark Krikorian, the executive director of the Center for Immigration Studies, a group that supports reduced immigration to the US, told CNN at the time that he sensed that the White House was “impatient with the pace of his activities.”

“The problem is that there’s all kinds of obstacles the system is dealing with,” he said.

That support seems to have only briefly extended his tenure within the administration.