The University and College Union instructed members in pre-1992 universities to begin "work-to-contract" industrial action - working minimum hours and refusing voluntary duties - on 10 October.
The action is in protest at employer-driven changes to pensions in the £30 billion Universities Superannuation Scheme, whose 130,000 active members are academics and senior administrators working in the UK's older universities, in the main.
Sally Hunt, the UCU general secretary, has said that if the employers do not return to the negotiating table, further options include rolling strikes and a boycott of the research excellence framework and student assessment.
Liam Burns, president of the NUS, said this week that the body had a long history of working closely with the UCU and supported it fully in its attempts to restart negotiations on pensions reform.
But he added: "There is no need for further or escalated action if employers are willing to return to the table and find an acceptable solution.
"Both sides must consider the impact on students and work towards a quick resolution."
He warned: "Any action that threatens students' ability to progress from year to year, or graduate at all, will immediately lose student support."
The NUS recently closed its own final-salary pension scheme for students' union officers.
Ms Hunt has always sought NUS support, and any student opposition to industrial action would weaken the UCU's position.
The changes to the USS, introduced on 1 October, have placed new members on lower-value career-average schemes, while existing members stay on final-salary deals.
At a press briefing last week, Ms Hunt outlined the key areas where the union wants the employers to return to negotiations.
She said that these included accrual rates in the section for new members and redundancy payments for staff at the ages of 50 and 55.
A spokesman for Universities UK, which represents the employers in the USS, said the pension scheme's joint negotiating committee "would welcome proposals for discussion from the UCU at its next meeting on October".
A spokesman for the Universities and Colleges Employers Association said of the work-to-contract action: "There has been no report from institutions of any impact at this early stage."