Christian Horner says Red Bull is now in a critical situation as it approaches the end of September without an engine supply deal in place for 2016.
Red Bull has threatened to quit the sport if it cannot secure a competitive power unit for next season when it plans to split with current supplier Renault. Mercedes has made clear that it will not supply the four-time world champions, leaving Ferrari as the only option for 2016.
However, it is unlikely Red Bull will get complete engine parity with the works team, such as the latest upgrades as soon as they arrive on the Ferrari and the latest developments in software, fuel and lubricants. Current Ferrari customer Sauber, for example, waited until the Belgian Grand Prix before it ran updates that were on the cars of Sebastian Vettel and Kimi Raikkonen four races earlier in Canada. An even more extreme example is Manor, which uses year-old Ferrari engines, but is set to switch to Mercedes power in 2016.
Asked to specify what kind of deal is on the table, Ferrari team boss Maurizio Arrivabene refused to go into details.
"As you know, there is an offer and the offer matches their need," Arrivabene said. "I can say nothing more than this."
But for Horner a deal needs to be done soon and it needs to be for a "first-class" engine.
"The situation is quite critical because, as we sit here, we don't have an engine," Horner said in the Suzuka paddock on Sunday. "The important thing for us is to have a first-class engine. First of all, we need to conclude our situation with our current supplier [Renault], but I think Dietrich [Mateschitz, Red Bull owner] has made the situation very clear."
Red Bull junior team Toro Rosso also needs a replacement engine deal for the outgoing Renault power units. With development of next year's car well underway both teams need to know which engine they will be racing, but Horner said the situation is even more critical for Toro Rosso.
"We're already late, very late," Horner added. "For Toro Rosso, it is more critical than Red Bull Racing. It already was difficult two weeks ago... so we're very, very late."