President Donald Trump 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.

President Donald Trump has escalated his standoff with Harvard University, seeking another path to prevent international students from attending the school after a judge blocked an attempt to revoke Harvard’s ability to enroll international students.

The president escalated his feud with Harvard on Wednesday by signing an order that deems the entry of the university’s international students into the U.S. a national security threat.