The Higher Education Funding Council for England had expected to examine a draft of the letter - which sets out university funding for the next year - at its board meeting yesterday.
Hefce has now scheduled an emergency board meeting for 25 February, when it is expected to make crucial decisions on allocations for 2014-15.
Nick Clegg, the Liberal Democrat leader, is said to be insisting that student opportunity funding for the poorest students is a “red line” in talks on the Department for Business, Innovation and Skills budget.
Despite having been judged as “locked down” and safe after previous scares, student opportunity funding is said to have come under fresh pressure from the Treasury earlier this week.
The cut to the fund was expected to be less than 20 per cent after extra money was apparently found by the Treasury (initial plans said the £322 million fund would be scrapped entirely). But others in the sector are said to have argued that if extra money was available, it should fund other important areas.
At a recent Russell Group dinner, the merits of investing in Strategically Important but Vulnerable Subjects (which are mainly in science) over student opportunity funding were discussed, according to some in the sector.
This is said to have persuaded the Treasury and the chancellor, George Osborne, to “open up” discussions again on possible major cuts to student opportunity funding.
Mr Clegg was out of the country until Wednesday, after leading a business delegation to Colombia and Mexico, which caused further delays in the budget discussions. And on his return, he is said to have insisted that the fund will be protected from major cuts.
However, others in the sector say the debate has moved on since then, and student opportunity funding will be spared major cuts, with the sticking point now being the £41 million Access to Learning Fund.
There is also conflict between the Treasury and BIS over whether the grant letter should spell out to Hefce where the cuts should be made. The Treasury is said to have demanded detailed directions in the letter, while BIS is in favour of greater flexibility for Hefce.