President Donald Trump has signed a proclamation to suspend international visas for new students at Harvard University, the White House announced Wednesday, in a dramatic escalation of its efforts to block foreign nationals from enrolling at the elite university.

Trump’s proclamation marked his administration’s latest attempt to cut off Harvard from a quarter of its student body.

Harvard University expands its lawsuit against the Trump administration, challenging a new proclamation banning new foreign students from the university. A judge temporarily blocks ban on US entry of foreign nationals seeking to study at Harvard.