Honda has revealed that it has held talks with other Formula 1 teams over a possible supply of engines, but insists that nothing has been agreed.
The Japanese manufacturer has endured a troubled time since returning to the sport with McLaren in 2015, and pre-season problems have left it facing a big challenge to catch up this year.
As revealed earlier this month, McLaren has sounded out Mercedes about a possible supply of engines if it cannot sort out its situation with Honda.
But both the Woking-based team and Honda have insisted that they are fully committed to each other.
Speaking on Saturday in Melbourne, however, Honda boss Yusuke Hasegawa conceded for the first time that Honda has had contact with other teams.
"Of course a second team or third team, we have some conversations, but nothing is fixed," he said.
McLAREN AND MERCEDES RUMOURS PLAYED DOWN
McLaren boss Eric Boullier played down that his team was considering a return to Mercedes power.
Sources have indicated that talks with Mercedes have indeed taken place, but Boullier would not elaborate.
"Rumours are rumours, and I guess our performance, and especially during our testing sessions, have created such rumours," Boullier said. "No, there is no such.
"Obviously we are looking at every option to recover and catch up because we are definitely not in the position that we are expecting to be and we want to be.
"So with Honda we are working hard on this.
"Testing was obviously not very good, and obviously still today we can see that our pace is not good enough. But we are just working together."
Pressed on how long it would take to change to another power unit supplier, he said: "I'm not going to comment on these kinds of discussions. This is a private discussion.
"We are with Honda, we have to cover all options, that's it. All I can tell you is... nothing else, actually."
Hasegawa was equally reticent, saying: "Also the same, the rumours is just a rumour.
"Obviously after the winter test we are having a strong pressure from the team and from the drivers. We try to keep improving."