Overseas students who enrolled on University of Hertfordshire courses last September must settle their debts on Monday or risk being suspended.
An email to a student, sent last week and seen by BBC News, gives a deadline of 24 August for 100% payment.
The university says it has already extended its payment deadlines.
Hundreds of overseas students from several universities have been relying on food banks since part-time work and family funding ran low during lockdown.
Charity workers who have been helping the students say, of the universities they have been negotiating with, the deadline set by the Hatfield-based institution is currently the earliest.
The university says the extended debt-payment deadlines are pegged to students' enrolment dates.
"We amended our payment dates to give all students more time to pay both their accommodation and tuition fees - for example, agreed payment plans with students until next enrolment milestone," it said.
Students who started their courses in January had until December to pay, the university said.
Another letter, sent earlier this month, talks of a student's access to the university's academic website being withdrawn but says a decision was made to allow them to continue their studies and the block removed.
"However, if your debt remains and the final instalment of your tuition fees, which are due 24 August 2020, are not paid, you will be debt chased," it says.
"Your StudyNet will be blocked and you may be withdrawn from your course, if your fees remain unpaid."
A spokeswoman for the university confirmed on Friday that nothing had changed in the past few days.
But she added: "We are happy to discuss and put payment plans in place for any students affected, to give them more time to repay."
Newham Community Project, in east London, has been providing food parcels to about 600 students during the pandemic, most in their early 20s and from India.
Many are taking master's degrees and fear being unable to complete their education.
The pandemic has disrupted studies across higher education in the UK, with closed campuses ending access to labs and libraries and tuition moving online.
International students have to prove they have the funds to cover rent, fees and living expenses before being granted visas.
If they are studying full time at bachelor's level or higher at a UK university, they are usually allowed to work up to 20 hours a week, under Home Office guidance.
Covid-19 means many have lost these part-time jobs, while their families in countries with their own outbreaks can struggle to send money - but international students have no recourse to public funds in the UK.
Laqab Mohammed, of Newham Community Project, has helped more than 300 students negotiate with their universities.
"Covid 19 has really brutally hit them in the sense that they have come to a foreign country with hopes and aspirations, to further their education and their careers, but it's derailed their plans effectively," he told BBC News.
"Their sponsors and their family businesses have been basically frozen.
"They don't have the money or the support network."
He is concerned part-time work is still scarce and some of the revised payment deadlines do not allow students the leeway to recover financially.
Of the 18 universities where Newham Community Project has intervened, most have agreed flexible payment plans with deadlines late this year or early next.
University of Hertfordshire said it "has been acutely aware of the impact the pandemic has put some students into financial hardship" and had directly responded in a number of practical ways to support them, including:
- immediate non-repayable grants from a new Covid-19 relief fund
- amended payment dates to the next enrolment milestone
- rent refunds to students who had moved off campus
"We would urge students experiencing any financial difficulties to please contact the university's student account management directly to discuss their circumstances and to agree a resolution," it added.
Newham Community Project said Anglia Ruskin University, which had been asking for payment by July, was among those to have granted extended payment plans.
A 15 September payment deadline is, however, looming for 155 University of East London students, also being represented by the charity.