The US has ordered its embassies around the world to stop scheduling appointments for new student visas.

The memo from the US State Department said it was preparing for an “expansion of required social media screening and vetting” applicable to all student visa applications.

This is the latest move that takes aim at international students, a major source of revenue for US universities.

US State Secretary Marco Rubio recently rescinded hundreds of visas and the Trump administration moved to stop Harvard University from admitting any non-Americans.

Universities have accused the Trump administration of trying to infringe on free speech and critics say the new policy on social media vetting represents a further violation of the rights that are supposed to be enshrined by the First Amendment in the US Constitution.