Niki Lauda says he would "veto" a supply of customer Mercedes engines for struggling former F1 grandee McLaren.
Although consistently denied, persistent rumours have said the beleaguered British team’s patience with Honda is finally up.
But Toto Wolff, the Mercedes chief, denies the solution will be as simple as a reunion of the old McLaren-Mercedes name.
"It’s important for formula one that Honda remains," he said. "I have no doubt that they will solve their problems."
And Mercedes team chairman Lauda’s denial is even clearer.
When asked about a potential McLaren-Mercedes deal, he said: "I would veto it. Two years ago, I pleaded for us to give Red Bull our engines.
"But I wouldn’t do it today. We have to concentrate fully on our duel with Ferrari rather than upgrading another of our rivals," the F1 legend told Auto Motor und Sport.
A McLaren-Mercedes deal also seems to have been ruled out by the sporting regulations, which require engine changes for the following season to be registered with the FIA by 15 May.