Comcast and Twenty-First Century Fox face a quick-fire auction for British broadcaster Sky on Saturday after neither side backed down in a drawn-out $34 billion battle.

A deadline set by a UK regulator for the two media companies to declare that their all-cash offers for Sky would not be increased passed on Friday without a move by either side — triggering a rare auction run by Britain’s Takeover Panel.

Fox, with the backing of partner Disney, and Comcast are vying for control of Sky to bolster their businesses in the face of rapid growth of streaming services such as Netflix, which are transforming the media industry.

Saturday’s auction of pay-TV group Sky will last a maximum of three rounds and any bids will be made in private by either telephone or e-mail, a source with knowledge of the process said.

The Takeover Panel then expects to announce the offer prices that the bidders have submitted on Saturday evening.

Comcast currently has the highest bid at $34 billion.