The development was announced by the Takeover Panel, which presides over City rules governing bids for United Kingdom firms, as the clock ticks down to its deadline for American suitors 21st Century Fox and Comcast (Swiss: CMCSA.SW - news) to make final offers for the UK-based home and mobile entertainment and communications company.
Comcast now has the upper hand in the bidding war after it made a 14.75 pound a share offer for Sky in July, which trumped an earlier 14 pound a share bid by Fox. Fox has bid $32.5 billion for the 61 percent of the satellite broadcaster it does not own. Comcast made its first bid in April before upping its offer to $34 billion in July, topping 21st Century Fox's bid.
The U.K. broadcaster is now valued at £27 billion, which translates to more than $35 billion.
Comcast, which owns the parent company of NBC News, NBCUniversal, now leads Fox in the fight with a $34.3 billion offer.
Fox last month gave itself the option of lowering the bar for approval for its bid to as little as 50 percent of Sky, meaning it needs just 11 percent more.
It would also provide access to Sky's entry into the gaming market.
An auction for Sky, which broadcasts to 23 million households across Europe, would be the biggest ever deal in the United Kingdom to be decided by a panel-run auction.
The news follows a report by Bloomberg that the takeover battle for Sky SKY-GB would likely be transferred to an auction. The auction will formally begin at 5pm on Friday and conclude at the. The rules allow for the suitors' final bids to be equal.
For Comcast, Sky offers a chance for growth - a company with proven quality in sports and entertainment together with the technology to deliver it. They will do so knowing what their rival has done in the previous round, a source close to the process said.
Fox has faced heavy scrutiny from the UK Government and competition watchdogs over its Sky takeover plans, while Comcast's bid was cleared by regulators early on in the process.
The battle for Sky is set to go to an auction, which will be settled Saturday.