Mercedes motorsport boss Toto Wolff has not ruled out the possibility of Formula 1 "enemy" Red Bull becoming a future engine customer amid negotiations over a deal involving Aston Martin.
AUTOSPORT and its sister publication Autocar revealed on Saturday that Aston Martin is discussing a return to F1 in a tie-up with Red Bull that would bring the team Mercedes engines.
The suggestion is Aston Martin would become a brand partner with Red Bull, in exchange for brokering a deal with Mercedes.
Red Bull's current supply contract with Renault is due to expire at the end of next year, with the French manufacturer rumoured to be on the brink of re-establishing its own team.
A Renault takeover of its former squad Lotus - which currently runs Mercedes power - is mooted, potentially releasing a Mercedes customer engine supply for Red Bull, in a partnership previously considered unthinkable.
Asked by AUTOSPORT about the possibility of a Red Bull-Mercedes deal, Wolff replied: "There are many things to be considered.
"What happens if Renault decides to have its own team, to buy another team?
"Will they continue to supply Toro Rosso and Red Bull?
"If not, what are the solutions? Who is going to supply them to make them stay in the sport?
"What does it mean for us? Until now they have been the enemy.
"Maybe there is a new enemy. What does it mean in terms of politics, in the grand scheme of things?"
Although Wolff maintained no talks have yet commenced, he said the door was 'open'.
"There are no discussions ongoing, nothing has been started, but you need to consider all the options," he said.
"I'm leaving the door open."
Red Bull team principal Christian Horner, meanwhile, refused to dismiss the prospect of a Mercedes tie-in in the future.
"Andy Palmer was here this weekend on a Force India pass," said Horner, referring to the Aston Martin boss's attendance at Silverstone for the British Grand Prix.
"The fact is, we have a contract with Infiniti and Renault until the end of 2016. Anything beyond that is pure speculation.
"Last week it was Ferrari, this week it's Aston Martin, next week it will probably be Honda or Lamborghini.
"We have a contract and commitment with Infiniti, a very good relationship with Infiniti, and anything beyond the end of 2016 is purely speculative."
Asked whether he had at least spoken to Aston about a deal, Horner again declined the opportunity to quash the speculation, replying: "I speak to lots of people."