Harvard students weave through tree-lined streets and redbrick campus buildings, but beneath the veneer of daily life fear has taken root: the most prestigious university in the United States is bracing for an "assault" by President Donald Trump.

Since returning to the White House, Trump has targeted prestigious universities, alleging anti-Semitism and liberal bias – with Harvard a primary quarry.

He has launched what one academic called a "blitzkrieg" of measures – arresting overseas students and researchers, slashing federal funding, and seeking to end Harvard's tax-exempt status.

"It's what they deserve!" Trump wrote on his Truth Social platform on Friday.

Unlike other universities that have bowed in recent days, Harvard defied Trump – suing his administration and mounting a fightback praised by students, faculty and commentators.

"This is not about scalping [Harvard]. This is about blitzkrieg and bringing out the biggest guns that you have," said Sheila Jasanoff, a Harvard Kennedy School professor.

"There's been essentially no check to the appetite of this administration."

First-year student Feodora Douplitzky-Lunati said "there's a lot more wariness" among foreign students who fear they could be caught in immigration raids like those at Tufts and Columbia.

Signs have advised international students not to discuss visa status, said Douplitzky-Lunati, who plans to study Slavic studies and economics.

Harvard researcher Kseniia Petrova has been detained since February, after her visa was revoked returning from France.

Students involved in pro-Palestinian protests following the October 7, 2023, attacks on Israel and the Gaza conflict have been arrested and slated for deportation at other campuses.

Trump's team imposed an April 30 deadline for universities to hand over international student data or risk losing a key certification to sponsor international students – affecting 27 percent of Harvard's student body.

In an email, Harvard said it complied but encouraged students to focus on their studies.

Many foreign students face the dilemma of leaving for summer break and risking being denied re-entry to the United States.

Alongside visa measures, Trump has targeted Harvard's finances.

He put US$9 billion in federal funding under review, ultimately freezing US$2.2 billion in grants and US$60 million in contracts in an opening salvo.

Harvard imposed a hiring freeze, some researchers received stop-work orders, and its Chan School of Public Health was particularly exposed to the cuts.

"The administration have been much more aggressive than anyone anticipated. There's going to be chaos. The staff will get smaller," said one casualty of the cuts who suggested US HIV and tuberculosis cases would increase as a result.

Harvard president Alan Garber said Wednesday the university's endowment cannot legally offset shortfalls caused by Trump.

"It is an assault on higher education. We must join not only with the rest of the academic community, but with civil society," he said according to an alum on the call.

Another said Garber described the situation as a long, existential battle and appealed for alumni donations. (AFP)