The energy drink company's motor sport adviser Helmut Marko said at Interlagos that the decision had been
delayed for about another week, but Germany's Auto Motor und Sport reports that Abu Dhabi is actually the new deadline.
The magazine said the FIA has now approved the application for a fourth Mercedes engine supply, but the German marque's exclusive partner McLaren is currently vetoing the Red Bull deal.
It is said that McLaren's decision hinges on Mercedes' precise plans for a closer involvement with Brawn, but Marko said: "Time is running out."
With Mercedes out of the picture, Red Bull's choice is between either staying with Renault or - like Williams - switching to Cosworth.
Renault, also with a works team, is said to be pushing hard to retain its competitive partner, perhaps promising to bundle a sponsorship deal with the oil company Total.
