Washington, May 28 (AP) New US State Department guidance on visa applications is adding to scrutiny of international students that has intensified under President Donald Trump, who has leveraged control of foreign enrolment to press his demands with American colleges.

In a cable sent Tuesday to US embassies and consulates, Secretary of State Marco Rubio halted the scheduling of new visa interviews for international students until the department releases guidelines for increased vetting of their activity on social media.

Existing appointments may be kept and will proceed under current review guidelines, the cable said, but new guidance is expected in the coming days.

It came days after the Trump administration moved to block Harvard University from enrolling any international students, a decision that has been put on hold by a federal judge, pending a lawsuit.

Trump said on Wednesday that Harvard, whose current student population is made up of more than a quarter of international students, should limit that percentage to about 15 per cent.

“I want to make sure the foreign students are people that can love our country,” Trump told reporters in the Oval Office.

Earlier this year, US Immigration and Customs Enforcement arrested and tried to deport students who had been involved in campus protests against the Israel-Hamas war.

And the Trump administration abruptly terminated the legal status of thousands of international students before reversing itself and then expanding the grounds on which students can lose permission to study in the US.

The uncertainty raised by the suspension of visa appointments will do further damage to the US reputation as a destination country, said Fanta Aw, CEO of NAFSA, an association that represents international educators.

Students generally commit to their programme of study in late spring, meaning now would be peak time for students to schedule their visa interviews.

“International students and scholars are tremendous assets that contribute to US preeminence in innovation, research, and economic strength,” Aw said in a statement.

“Undermining their ability to study here is self-defeating. With these actions, the United States will alienate the very minds that fuel its success.” At the University of Wisconsin-Madison, the climate of uncertainty led one international student to cancel a trip home to Vietnam this summer.

He emails the school's international office frequently to make sure his legal status is secure.

“There's just this constant unease. It's quite stressful, really. I try not to think about too much or else I get too anxious,” said the student, who spoke on condition of anonymity out of fear of being targeted.

The pause affects three categories of visas that cover university students, as well as high school exchange students and boarding school students.

The largest category, F-1 visas, includes students who are enrolling at full-time accredited schools.

Students participating in exchange programmes enter on J-1 visas, and those enrolling in vocational or non-academic programmes enter on M-1 visas.

Around 1.1 million international students were in the United States last year -- a source of essential revenue for tuition-driven colleges.

International students are not eligible for federal financial aid. Often, they pay full price.

Northeastern University, which has more than 20,000 international students, has set up “contingency plans” for those hit by visa delays, said spokeswoman Renata Nyul, without elaborating.

“This is a very dynamic situation, and we are closely monitoring the developments in real time to assess any potential impacts,” she said.

Visa applicants have been required to provide social media handles to the State Department since 2019. The cable did not indicate what kind of additional scrutiny the new guidelines would cover, but suggested the new reviews may be more resource-intensive.

The additional vetting will deter students from coming to the US, said Jonathan Friedman of PEN America, a literary and free expression organisation.

“The details remain vague, but this policy risks upending the long-standing place of the US as a beacon for intellectual and cultural exchange with the world,” Friedman said.

The move to cut off international enrolment at Harvard stems from a dispute with the Department of Homeland Security, which has demanded that it provide information about foreign students that might implicate them in violence or protests that could lead to their deportation.

Harvard says it complied with the records request, but the agency said its response fell short.

On Wednesday, Trump said more scrutiny of Harvard's students is necessary.

“They're taking people from areas of the world that are very radicalised, and we don't want them making trouble in our country,” Trump said.

The Trump administration has cut over USD 2.6 billion in federal grants for Harvard as it presses demands for changes to policies and governance at the Ivy League school, which the president has described as a hotbed of liberalism and antisemitism.

Harvard has pushed back and filed a lawsuit against the administration. (AP) ARI