US President Donald Trump defended on Sunday his administration’s move to block foreign students at Harvard after a judge suspended the action, branded by the top university as unlawful.

“Why isn’t Harvard saying that almost 31 [per cent] of their students are from foreign lands, and yet those countries, some not at all friendly to the United States, pay nothing toward their student’s education, nor do they ever intend to,” Trump posted on his Truth Social platform.

“We want to know who those foreign students are, a reasonable request since we give Harvard billions of dollars, but Harvard isn’t exactly forthcoming.”

Homeland Security Secretary Kristi Noem on Thursday revoked Harvard’s ability to enrol foreign nationals, throwing the future of thousands of students and the lucrative income stream they provide into doubt.

She had threatened last month to block international students at the school unless it turned over records on visa holders’ “illegal and violent activities”.

But a judge quickly suspended the move after the university sued to “stop the government’s arbitrary, capricious, unlawful and unconstitutional action”.

The White House is cracking down on US universities on several fronts, justified as a reaction to what the administration says is uncontrolled anti-Semitism and a need to reverse diversity programmes aimed at addressing historical oppression of minorities.

It has also moved to revoke visas and deport foreign students involved in protests against Israel’s military offensive in Gaza, accusing them of supporting Palestinian group Hamas.

At Harvard, the government has threatened to put $9 billion of funding under review, then went on to freeze a first tranche of $2.2bn of grants and $60 million of official contracts. It has also targeted a Harvard Medical School researcher for deportation.

The loss of foreign nationals — more than a quarter of its student body —could prove costly to Harvard, which charges tens of thousands of dollars a year in tuition.

Harvard is the wealthiest US university with an endowment valued at $53.2bn in 2024.