Honda ceased its official works involvement in the sport at the end of last season, and henceforth Red Bull is paying for its services, including the development of this year's power unit for the move from E5 to E10 fuel.
The original strategy as announced late last year was that the new Red Bull Powertrains division would take complete power units from Honda, with full engineering support at the tracks, only in 2022.
Once RBP had got up to speed it would then build the engines from Honda parts at its Milton Keynes facility in 2023, 2024 and 2025 while simultaneously working on its own project for the new F1 rules that come into force in 2026.
However Red Bull motorsport boss Helmut Marko has revealed that the plan has changed, and the intention now is that Honda will continue to supply complete engines from Japan to Red Bull and AlphaTauri until the end of 2025.
The decision removes any concerns about issues such as quality control that might result from moving the building of the power units to the UK, while also freeing up RBP to focus more on its 2026 project.
The change has been made in part to ensure that RBP will still be a new participant when its own engine is introduced in 2026.
It will thus benefit from the concessions that are being discussed mainly to help encourage the VW Group to finally commit to F1, such as a higher power unit budget cap.
It's understood that details of the new arrangements have yet to be finalised, and it's not clear yet whether the engines will still be badged as Hondas until 2025, although such a move would be logical given the desire to ensure that RBP is a new participant in 2026.
"We have now also found a completely different solution to the one originally envisaged," Marko told Autorevue magazine.
"The engines will be manufactured in Japan until 2025, we will not touch them at all. That means that the rights and all these things will remain with the Japanese, which is important for 2026 because it makes us newcomers.
Marko suggested that winning the 2021 world championship has encouraged Honda to remain closer to F1 than had been expected.
"In the course of our ever greater successes, a certain rethinking has taken place among the Japanese. And also that they could of course use the battery knowledge for their electrification phase.
"It was initially planned that they would only make our motors for 2022. Now it has been decided that this will continue until 2025, which is of course a huge advantage for us. This means we only have to make fine adjustments and calibrations."
Regarding the building up of the RBP facility, he added: "The prerequisite for this agreement was that engine development was frozen. Because the first phase would have been that we do everything ourselves. That's why we started in Milton Keynes and dutifully bought in from [dyno supplier] AVL.
"The plant will go into full operation in May/June. The final decision to do it ourselves was conditional on everything being frozen. Because otherwise we wouldn't have had a chance with this complex thing."
Meanwhile as reported on Wednesday former Honda F1 boss Masashi Yamamoto has left the manufacturer to set up his own consultancy in order to provide a bridge between Red Bull and Japan, further extending the continuity between the partners.
