Harvard responded swiftly on Thursday to President Trump’s new order banning the enrollment of international students at the university, and was expected to ask a federal judge to immediately block it.

The White House order, issued at 8 p.m. on Wednesday, was the third time in the past month that the Trump administration has tried to use its power to ban international enrollment at Harvard in what the university has said is a violation of its First Amendment rights.

The White House’s proclamation appeared to be an effort to work around a court order that has blocked the earlier bans, and it was the first time Mr. Trump had directly invoked the executive power of the presidency against Harvard.

The president’s order appeared to affect only newly arriving international students at Harvard, including about 300 first-year students who are set to begin classes this fall. It was unclear how many newly arriving graduate students are international.

Mr. Trump, in the same proclamation, also urged Secretary of State Marco Rubio to consider revoking current visas for Harvard students, a move that would affect the school’s entire international enrollment.

An estimated 5,000 international students are currently enrolled at Harvard and another 2,000 recent graduates are in the United States on visas permitting students to remain temporarily after graduation to work.

The earlier ban attempts had been issued by the Department of Homeland Security and have been temporarily blocked by Judge Allison D. Burroughs of the Federal District Court in Boston, where Harvard has filed two lawsuits against the administration.

In a statement Wednesday night, Harvard vowed to protect its international students.

Kirsten Weld, president of the Harvard chapter of the American Association of University Professors, said the Trump administration’s order “wreaks havoc on the lives of thousands of young people.”

The school has become a focal point of the administration’s effort to conform higher education with Mr. Trump’s political agenda, one originally focused on antisemitism, but now broadened to attack diversity, equity and inclusion programs and transgender athletes.

“I have determined that the entry of the class of foreign nationals described above is detrimental to the interests of the United States,” Mr. Trump wrote in the proclamation, “because, in my judgment, Harvard’s conduct has rendered it an unsuitable destination for foreign students and researchers.”

This story is developing. Check back for updates.