US consular officers are now required to conduct a "comprehensive and thorough vetting" of all student and exchange visitor applicants to identify those who "bear hostile attitudes toward our citizens, culture, government, institutions, or founding principles," said the cable, which was dated June 18 and sent to US missions on Wednesday.

On May 27, the Trump administration ordered its missions abroad to stop scheduling new appointments for student and exchange visitor visa applicants, saying the State Department was set to expand social media vetting of foreign students.

US Secretary of State Marco Rubio had said updated guidance would be released once a review was completed.

The June 18 dated cable, which was sent by Rubio and sent to all US diplomatic missions, directed officers to look for "applicants who demonstrate a history of political activism, especially when it is associated with violence or with the views and activities described above, you must consider the likelihood they would continue such activity in the United States."

The cable, which was first reported by Free Press, also authorized the consular officers to ask the applicants to make all of their social media accounts public.

"Remind the applicant that limited access to [...] online presence could be construed as an effort to evade or hide certain activity," the cable said.

The move follows the administration's enhanced vetting measures last month for visa applicants looking to travel to Harvard University for any purpose, in what a separate State Department cable said would serve as a pilot program for wider expanded screening.

Online presence

The new vetting process should include a review of the applicant's entire online presence and not just social media activity, the cable said, urging the officers to use any "appropriate search engines or other online resources."

During the vetting, the directive asks officers to look for any potentially derogatory information about the applicant.

"For example, during an online presence search, you might discover on social media that an applicant endorsed Hamas or its activities," the cable says, adding that may be a reason for ineligibility.

Rubio, Trump's top diplomat and national security adviser, has said he has revoked the visas of hundreds, perhaps thousands of people, including students, because they got involved in activities that he said went against US foreign policy priorities.

Those activities include support for Palestinians and criticism of Israel's conduct in the war in Gaza.

A Tufts University student from Turkey was held for over six weeks in an immigration detention center in Louisiana after co-writing an opinion piece criticizing her school's response to Israel's war in Gaza. She was released from custody after a federal judge granted her bail.

Trump's critics have said the administration's actions are an attack on free speech rights under the First Amendment of the US Constitution.

Fewer appointments?

While the new directive allows posts to resume scheduling for student and exchange visa applicants, it is warning the officers that there may have to be fewer appointments due to the demands of more extensive vetting.

"Posts should consider overall scheduling volume and the resource demands of appropriate vetting; posts might need to schedule fewer FMJ cases than they did previously," the cable said, referring to the relevant visa types.

The directive has also asked posts to prioritize among expedited visa appointments of foreign-born physicians participating in a medical program through exchange visas, as well as student applicants looking to study in a US university where international students constitute less than 15 percent of the total.

At Harvard, the oldest and wealthiest US university on which the administration has launched a multifront attack by freezing its billions of dollars of grants and other funding, foreign students last year made up about 27 percent of the total student population.

The cable is asking the overseas posts to implement these vetting procedures within five business days.