Honda wants clarity over future plans for engine development in Formula 1 before committing to the sport beyond 2021, according to Red Bull team boss Christian Horner.

Honda announced earlier this week that it would be extending its agreements with both Red Bull and sister team Toro Rosso until the end of the 2021 season, having initially agreed to work with both teams through to 2020.

This year has seen Honda enjoy its most successful season since returning to the sport as an engine supplier in 2015, scoring three wins through Max Verstappen at Red Bull.

But Horner explained to Sky Sports that greater clarity was required from F1’s bosses on plans for future engine development and possible freezes before Honda would commit to a longer-term deal.

“It’s great news that they’ve committed beyond 2020, so we’ve got a minimum of two years that we’re absolutely fixed on,” Horner said.

“They’re just waiting to see what are the regulations that are going to come in either for 2021, or primarily ’22 with regards to homologation or engine freezes to get the costs down.

“These engines are enormously expensive, and the technology involved. I think all the manufacturers together want to see some cost reduction in that area.

“We’re talking about the future. The discussion wasn’t just about ’21. There’s a real appetite there to build on what we’ve achieved so far in this relationship. It’s a great partnership between Red Bull and Honda as we’ve seen this year.

“I think the key aspect moving forward is absolute clarity on those rules.”

Horner was full of praise for the first year of Red Bull’s partnership with Honda, having ended the team’s long-term deal with Renault in order to link up with the Japanese manufacturer.

“Three victories this year, could have potentially been more, two pole positions - three that we achieved but didn’t start from pole on one of those three occasions - it’s been a great year for them,” Horner said.

“The reliability has been better, the performance has been getting stronger and stronger. You can see that in motion with the pride, the passion that exists within Honda. It’s great to see and great to be part of.

“It’s very easy to embrace people that are enjoying and sharing the same goals and objectives. That’s been a great journey this year. It’s a very different relationship, very different partnership.”