Dr Helmut Marko is planning a trip to Japan to continue "negotiations" with Honda about the 2026 season and beyond.
It comes after advanced talks about a 50 percent buy-out of the dominant Red Bull team were confirmed to have collapsed.
Marko, who is Red Bull's top Austrian official reporting to owner Dietrich Mateschitz, also ruled out any involvement by Porsche in the team's new 'Red Bull Powertrains" subsidiary.
"No, that's over too," he told Osterreich newspaper.
"The first engine we developed has already run on the test bench, so we're doing very well for ourselves there too."
Currently, although not branded as such, Red Bull's Honda-based engines are still being supported on a technical and supply basis by the Japanese carmaker.
But a full works return for Honda is now on the cards.
"That is being negotiated," Marko said. "I will be flying to Tokyo between the Singapore and Suzuka races in early October."
One rumour is that the Porsche collaboration was ultimately called off because Red Bull's billionaire owner Mateschitz, 78, is suffering from health problems and could not oversee the talks.
"It had nothing to do with that," Marko, who also denied that Mateschitz's son Mark is getting increasingly involved with the F1 team as a result, insisted.
"No," Marko added. "But Mark is coming to Monza today."
Although Ferrari's Charles Leclerc is on pole, Marko thinks victory for runaway world championship leader Max Verstappen is possible even despite his grid penalty.
"Unfortunately, we cannot take the Ferrari anniversary into account if we want to become world champions," the Austrian smiled.
"The chances of Max winning for the first time in Monza are good. He doesn't make mistakes and with our bigger wing we slide less than the others. We were the best in race trim."
Indeed, Dutchman Verstappen could theoretically wrap up his second consecutive drivers' title next time out in Singapore.
"In terms of the party environment, Singapore wouldn't be bad at all," Marko smiled. "But in terms of our engine partner Honda, Suzuka would be even better a week later."
