In a surprising twist in the Red Bull engine saga, Honda has emerged as the latest candidate to supply power units to the team.

With Ferrari and Mercedes having ruled out a deal with Red Bull, and with Renault having said it would be hard to say with the Milton Keynes team, Honda now appears to be the leading contender.

The Japanese manufacturer had said in the past that it was not willing to supply to more than one team in 2016.

Horner, however, refused to deny the speculation linking Red Bull with Honda.

"I think so far we have had the rumour for every since engine supplier mentioned in the back of our car for next year, so they have a 25 per cent chance, looking at it that way," Horner said in Austin on Friday.

"I think there is so much speculation and a lot of opinions being based on it.

"When we have something to say and something fixed you will be the first to know. It is being worked on really hard at the moment."

Horner admitted time was running out for Red Bull to find an engine and that a decision was needed quickly.

"It is getting tight," he said. "We have a great group of people. They are very adaptive, doing what they can with the information they have.

"At the moment they are coping very well with that."