The battle between 21st Century Fox and Comcast for media giant Sky will be decided by a three-round auction on Saturday unless a clear winner emerges before then, the Takeover Panel has confirmed.
It will go to an auction unless one side submits its "final and best offer" or drops out by 5pm on Saturday, which is unlikely.
In a statement, the Takeover Panel said the auction will consist of three rounds of bidding which will all take place on Saturday 22 September.
The auction will officially open at 5pm tomorrow, and will be brought to a close during the evening on Saturday. A winner will then be announced by 7am on Monday, when both companies have to confirm their offers.
The first round will give the company with the lower offer, currently Fox, the chance to increase its bid. The party who hasn't submitted a bid yet will get a chance to counter and increase its own bid in the second round. If the process is not concluded in the second round (if Comcast does not increase its offer) the auction will come down to a final round where both companies can make an increased bid.
The Takeover Panel will then announce the results of the auction in the evening.
Fox is offering £24.5bn for Sky, while Comcast is ahead with a bid of £26bn. Sky shares are currently trading slightly above this, valuing the company at around £27.1bn.
It is highly unusual for the takeover battle of such a large public company to come down to an auction of this kind.
The saga has been ongoing since December 2016, when Fox offered £10.75 per share for the 61 per cent of the business he did not already own.
But in February this year, Comcast tabled its own £12.50 bid, prompting Fox to up its offer to £14 in July, before Comcast raised its offer again just days later to £14.75.
The Takeover Panel said the auction was necessary in order to: "provide an orderly framework for the resolution of this competitive situation".