Mitchells & Butlers (M&B) will this week demand the Takeover Panel impose a 'put up or shut up' deadline on R20, which is believed to preparing to bid for the group.
M&B would not comment on weekend press reports that suggested that it would be seeking a deadline of April 24.
However the Publican understands the managed bar group will indeed lodge such a request with the City watchdog before the end of this week.
M&B has been in talks with shareholders who have indicated they would not wish to sell their holdings "disadvantageously".
Analysts have noted recently that R20, Robert Tchenguiz's investment vehicle that owns the Laurel Pub Company, will need to offer more than 550p to have any chance of securing serious interest from M&B investors.
R20 has been circling M&B for some weeks and many observers anticipate an indicative bid within the next ten days.