With speculation pointing at a buyout by the German manufacturer of current engine customer Brawn, it had been suggested that Red Bull might instead choose to stick with its Renault power plants.
But after qualifying at Monza, boss Horner told the German broadcaster RTL: "(Mercedes powered) Force India is in some unbelievable form, but there are six Mercedes engines in the top seven.
"For sure that is no coincidence," the Briton added. "Mercedes builds very good engines."
Also at Monza, Ross Brawn would not comment on the reports about Mercedes buying 75 per cent of his Brackley based team.
"I'm not going to comment on our specific plans, drivers, sponsors, they'll all be announced in due course.
"We're very comfortable with where we're going to be next year. That's as much as I would like to say," said Brawn.
08/25/09 (GMM) The signs are growing stronger that Red Bull is preparing to switch to Mercedes-Benz engine power for the 2010 season. The rumors were circulating prior to Sebastian Vettel suffering two Renault engine failures at Valencia last weekend.
Now team boss Christian Horner is quoted as saying by Bild newspaper: "We have several options (and) Mercedes is one."
Racing boss Norbert Haug, whose employer Mercedes already supplies the McLaren, Force India and Brawn teams, commented: "We want to decide in four weeks."
In a separate report, in the Austrian newspaper Salzburger Nachrichten, Red Bull's motor racing advisor Helmut Marko also raised the prospect of an engine change.
"There are good arguments both for extending with Renault and for changing to Mercedes," he said. "By the end of August we want to know."
Vettel's two engine failures at Valencia, for which Renault apologized, were on top of two additional failures earlier this season, Marko confirmed.
"Those are facts that one must consider," he acknowledged, "as well as the fact that all of the drivers with Mercedes this year have had no problems."
08/23/09 (GMM) An albeit irritated Christian Horner on Sunday denied the service provided by Renault at Valencia was the final straw in Red Bull's relationship with its French engine supplier.
It is well known that the Milton Keynes-based team was already contemplating switching suppliers for the 2010 season, and Renault's case was not strengthened this weekend as two engines fitted to the car of title challenger Sebastian Vettel's car failed.
It brings the German driver's tally of blown engines up to four for the season, causing Horner to surmise the "almost inevitable" prospect of ten-place penalties at the crucial tail-end of the championship calendar.
But the energy drink-owned team's boss said it is not right to assume that Red Bull and Renault will now definitely part at the end of the year.
"I think it is still a long way to go in this championship and obviously our options are open," Horner is quoted as saying by F1's official website.
"But you can't make a decision based on one weekend, you have to look at the whole season and Renault so far has given us a great service and support. It was really unfortunate to have two engine failures in one weekend," he added.
07/07/09 (GMM) Even at the apparent conclusion of the FIA-FOTA war, it seems Red Bull is still on the market for a new formula one engine supplier for 2010.
Earlier this year, the fact that Christian Horner openly mused not signing another customer contract with Renault was believed to be based on speculation that some carmakers may not be on next year's grid.
"Who knows what engine manufacturers are still going to be there in 2010?" the Red Bull boss said in April.
As the FOTA war ended late in June, however, part of the peace agreement was the manufacturers' commitment to F1 at least until the end of 2012.
"So in the past, if somebody was worried, maybe after Honda left or somebody else, not now," Luca di Montezemolo said.
But it seems Red Bull Racing, whose Renault contract runs out this year, is still considering switching to Mercedes power. Horner told the latest edition of Germany's Auto Bild: "The Mercedes engine is good, but there is no time pressure.
"Brawn demonstrated that it is possible to change engine even at a late stage," the Briton added.
07/06/09 There are rumors that Red Bull Racing may want to change engines next year with the suggestion being that the team could switch to Mercedes-Benz. The success of Brawn GP has shown that the engines are highly competitive and Mercedes-Benz is particularly interested in the team because it would give it access to rising German star Sebastian Vettel, who is otherwise tied into a Red Bull contract. Mercedes-Benz is keen to expand its engine supplies to avoid lay-offs in its engine division while at the same time strengthening its F1 position. Grandprix.com