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 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 foreigners from enrolling at the elite university.

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.