WASHINGTON — The director of the agency overseeing legal entry into the United States, including through green cards and asylum, was asked to resign from the agency on Friday, according to a letter sent out to the agency and obtained by NBC News.

L. Francis Cissna has served as President Trump’s only director of U.S. Citizenship and Immigration Services, an agency within the Department of Homeland Security. He oversaw the agency during the final iteration of the travel ban, attempts to repeal status for “Dreamers” and the administration’s repeated attempts to limit the ability for undocumented immigrants crossing the southern border from Central America to claim asylum.

USCIS is now on the verge of finalizing a rule to restrict legal immigrants who use public benefits from receiving green cards, or legal permanent residency.

Since the abrupt firing of former DHS Secretary Kirstjen Nielsen in April, Cissna’s departure has been rumored to follow. The White House, at the direction of senior adviser Stephen Miller, has been eliminating staff who are seen as out of step with more hardline policies.

Cissna will depart the agency on June 1, according to the letter he sent employees on Friday.

“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,” he said in the letter.

Prior to leading USCIS, Cissna served at DHS in the Office of Policy in the Obama administration and worked for Republican Senator Chuck Grassley.

According to a source familiar with Cissna’s resignation, Trump thanked him for his service and asked him to resign.

The news comes as the White House is expected to appoint Ken Cuccinelli, former attorney general of Virginia, to a top immigration policy position.