Red Bull boss Dietrich Mateschitz has given his team a new deadline to secure a competitive engine for the 2016 season.
Amid threats to withdraw from the sport entirely if a competitive engine cannot be sourced, Mateschitz says his team will have until the weekend of November 21-22 to secure its future.
The Milton Keynes outfit has been embroiled in a battle to tie up a new engine supplier after severing ties with Renault in September following an unsuccessful campaign.
An initial deadline was set for the end of October although the squad has been unable to conclude talks with suppliers.
“I extend the deadline for three more weeks,” said Mateschitz.
“The situation is clear, we won’t get any of the existing powertrains because all teams fear that we would be faster than their own works outfits.
“As we know you can’t buy courage or sporting spirit.”
Options appear to be fast running out for the Red Bull and Toro Rosso teams after failing to agree a deal with either Mercedes or Ferrari.
A switch to Honda emerged as a possibility at the Mexican Grand Prix, while there is hope the relationship with existing supplier Renault is not beyond repair.