Fox is not expected to stray from the £10.75-per-share value that it had previously agreed to informally with Sky.
It first emerged last Friday that Fox was in talks to acquire the 61 per cent of Sky it does not already own. The £10.75 offer would value Sky at around £18.5bn.
A previous takeover approach for Sky failed in 2011, at the height of the News of the World phone-hacking scandal and amid political and regulatory scrutiny.
A number of shareholders have been critical of the offer this week, with some saying it undervalues Sky and others questioning the position of Rupert Murdoch’s son, James, who is chief executive of Fox and chairman of Sky.
Fox declined to comment.