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.

The university called it “yet another illegal retaliatory step” from an administration that has sought ways to circumnavigate the courts in its push to bar foreign students.

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.