University leaders are lobbying for a return to campuses this month for all students in England - from 12 April rather than suggestions of 17 May.
Many students "feel they have been forgotten by government", said Tim Bradshaw, chief executive of the Russell Group of universities.
About a million students are still only studying online.
The Department for Education says return dates will be reviewed "by the end of the Easter holidays".
This timetable is understood to mean by the end of next week.
But students have been promised at least a week's notice, which would mean a decision for a return from 12 April would have to be announced over the Easter weekend.
'17 May at earliest'
Universities UK says "concerns are growing that the next stage of student returns will be delayed until 17 May at the earliest".
That would mean that many students, paying full fees and in some cases rent, would see their summer term on campus shrinking to a few weeks, before ending in June.
It would add pressure to calls for students to be given refunds after a second year of disruption.
While schools and colleges had a big back-to-school return in March, much of university teaching has remained off-campus and online, with no date for a return.
Some practical courses, requiring hands-on training, have returned, with Universities UK estimating that half of 2.1 million students do not have any indication of when they might go back.
In some universities, teaching is going to remain online for the rest of the academic year.
"There are university students across the country on courses such as business, maths and languages who are still waiting to find when - or even if - they will be able to return to in-person teaching this year," says Dr Bradshaw, head of the Russell Group of 24 leading research universities.
"We are particularly concerned about the impact on student mental health," he says.
Dr Bradshaw urged ministers to allow students to go back for in-person teaching from 12 April - arguing that there was little evidence that it would threaten a significant increase in infections.
A survey from the Higher Education Policy Institute found that two-thirds of students have been staying in their term-time accommodation, even if studying online, suggesting there would be less of a mass migration than at the start of the academic year.
"We have shared comprehensive evidence with the government on the clear benefits of a 12 April return to in-person activities for students' mental health and wellbeing," said a Universities UK spokeswoman.
Debra Humphris, chair of the University Alliance group of universities, said an earlier return would be particularly important for those students graduating this year - who want the "face-to-face employability support" before entering an "uncertain job market".
But the UCU lecturers' union has rejected calls for a campus return this month - saying it "smacks of self-interest and risks the safety of staff, students and the wider public".
Jo Grady, the union's general secretary, said "vice-chancellors lured students to university with the promise of a relatively normal campus experience, only for them to be left facing long periods in lockdown.
"Universities should not now be asking hundreds of thousands of students to return for in-person teaching after Easter when most courses will only have revision classes and exams left," said Dr Grady.
A Department for Education spokeswoman said: "We will be reviewing options for the timing of the return of all remaining students by the end of the Easter holidays.
"Decisions will take into account the need to protect progress across the wider roadmap out of the pandemic, including the spread of the virus in communities and pressures on the NHS."