US President Donald Trumps has said he wanted to assure Chinese international students in the country that they would be fine amid his administration's crackdown on academia.

Trump's administration said this week it would specifically target permissions for Chinese students in its latest broadside against US higher education.

But when asked late on Friday what message he would send to Chinese college students in the country, Trump insisted: "They're going to be ok. It's going to work out fine."

"We just want to check out the individual students we have. And that's true with all colleges," he said.

The softer tone comes after a judge on Thursday extended a temporary block on Trump's bid to prevent Harvard from enrolling international students.

US Secretary of State Marco Rubio vowed on Wednesday to "aggressively" revoke visas to students from China.

Rubio has already yanked thousands of visas, largely over students' involvement in activism critical of Israel's offensive in Gaza,but also over minor traffic violations and other infractions.

The Trump administration has been in an ongoing showdown with academia, and Harvard in particular, demanding it provide a list of students that the government is interested in, something the prestigious university has declined to do.

"I don't know why Harvard's not giving us the list. There's something going on because Harvard is not giving us a list," Trump said on Friday.

"They ought to give us a list and get themselves out of trouble," he insisted, suggesting that "they don't want to give the list because they have names on there that supposedly are quite bad."

International students on average make up just under six percent of the US university population – far below Britain, the second top destination for international students, where the figure is 25 percent.(AFP)