International students will be forced to leave the US or transfer to another university if their schools offer classes entirely online this autumn, federal immigration authorities said on Monday. "Non-immigrant F-1 and M-1 students attending schools operating entirely online may not take a full online course load and remain in the United States," the US Immigration and Custom Enforcement agency said. "Active students in the United States enrolled in such programmes must depart the country or take other measures, such as transferring to a school with in-person instruction to remain in lawful status. "If not, they may face immigration consequences including, but not limited to, the initiation of removal proceedings." The guidelines provide more pressure for campuses to reopen even amid growing concerns about the recent resurgence of coronavirus infections in the US. Universities received the guidance on the same day that some schools, including Harvard, announced that all instruction will be offered remotely. US President Donald Trump has insisted that schools and universities reopen lecture halls as soon as possible. After the guidance was released, Mr Trump repeated on Twitter that schools must reopen this autumn. Under the updated rules, international students must take at least some of their classes in person or leave the country. New visas will not be issued to students at universities or programmes that are entirely online. And even at those offering a mix of in-person and online courses this autumn, international students will be barred from taking all of their classes remotely. It creates an urgent dilemma for thousands of international students who became stranded in the US last spring after the coronavirus forced their universities to move online. Dozens of US colleges have announced plans to provide classes this autumn, but some have said it is too risky. Harvard on Monday said it would invite first-term students to live on campus, but classes would continue to be held online. The University of Southern California last week reversed plans to bring students back, saying classes would be “primarily or exclusively” online. The new guidance is likely to create “enormous confusion” among universities as they prepare for the term, said Terry Hartle, senior vice president of the American Council on Education, which represents university presidents. Of particular concern is a stipulation that international students would not be exempt from the rules even if an outbreak forces their schools to move online during the semester. Mr Hartle said it was unclear what would happen if a student ended up in that situation but faced travel restrictions from their home country. He said the immigration authorities were "clearly creating an incentive for institutions to reopen, regardless of whether or not the circumstances of the pandemic warrant it".