A string of internal deadlines have come and gone, so Red Bull is no longer trying to put a timeline on the decision about its engine supplier for the 2010 season.

It is no secret that the team would already have put pen to paper on a deal with Mercedes for 2010, having secured the clearance both of the German marque and the governing FIA.

But McLaren, Mercedes' exclusive F1 partner, is vetoing the arrangement, leaving Red Bull also weighing up a switch to Cosworth or staying with Renault power.

Mercedes' Norbert Haug confirmed: "We have no announcements planned for Abu Dhabi."

Asked when a decision will be made on the Red Bull side, the energy drink company's motor sport advisor Helmut Marko said: "Probably I would already have decided, but (designer Adrian) Newey is looking at all the options to the last detail.

"That's why we hired him," the Austrian told Auto Motor und Sport, "because he is satisfied with only the best."

Mercedes this year has proved the most powerful engine in F1, but the Renault is reportedly more fuel-efficient, which with the in-race refuelling ban next year will be important.

Cosworth, meanwhile, is the only engine maker currently allowed to be working on its 2010 unit, and it is thought Williams has made the switch believing that it will be the most powerful V8 on the grid next year.