Niki Lauda has said that no deal is in place between McLaren and Mercedes for 2018.
Amid intense speculation about McLaren's impending divorce from works partner Honda, new rumours suggest that the first McLaren-Mercedes tests may take place later this year.
However, Mercedes team chairman Lauda insists that no deal is in place.
"McLaren has a contract with Honda," he told German broadcaster Sky.
Lauda acknowledged the rumours of a McLaren-Honda split, but added: "That does not mean that a Mercedes engine is coming.
"No-one has asked."
In fact, he said that it is important that as "one of the top manufacturers in the world", Honda stays in F1.
"There was once the same topic [of a Mercedes deal] with Red Bull, but they stayed with Renault and the thing worked itself out," said Lauda.
McLaren's faltering season has seen them accrue just two points in 2017.