Max Verstappen believes the Honda engine is now "very close" to Mercedes in terms of performance.

Red Bull's decision to switch from Renault to the Japanese supplier was seen as a gamble despite the progress made with Toro Rosso in 2018.

But those fears were quickly dispelled with Verstappen claiming three wins thanks largely to Honda, who have done what seemed unthinkable during their McLaren days and largely caught up with the German manufacturer.

"We are very close to Mercedes," said Max via GPFans. "[Honda] have been working flat-out and the improvement we have made with the last two [engine upgrades] was a big one.

"What I think is also very positive is that we had a target throughout the year and we have always been at the same level or above the target, which we've never had before. So that's a good thing.

"[Honda] have always been very honest in what we would get, and sometimes we would even be a little bit better – which of course is even better!"

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As Mercedes and Ferrari have found, however, with every 10 horsepower that's found, finding the next 10 means getting more creative and Honda are also now finding that situation out for themselves.

“We could show our improvement, our good positive progress this year, not only with Red Bull but also Toro Rosso," technical director Toyoharu Tanabe told RACER.

“It was very nice for all the people working on this project and people in Honda, so I want to keep this momentum for next year. The development for next year has already started and then we need to push more to achieve our goal.

“I think it’s harder than in previous years. We need to be precise in every single area in terms of hardware, also software and then trackside management as well. So, we keep pushing.

"The PU means the ICE, MGU-H and K, and all the systems, water and oil. Also tools, software, we have a lot of things to do, but a big step? Maybe that’s getting difficult.”

Recently F1's top attention seeker Jacques Villeneuve told Motorsport-Total that Honda's reliability is still the main issue that would prevent Verstappen from challenging for the world title next year.

But after only one retirement caused by an engine issue during 2019, Max only wants the emphasis to be on one thing...

"More power!" he told Autocar. "The reliability has been really good this year, we've never retired because of a problem from their side, so for them, I think this season has been a breakthrough.

"Of course we had some victories already; they were really happy with that, I think it was a big boost for the whole company and they're very motivated."