Honda's Formula 1 chief Yusuke Hasegawa believes the gap between their engine and their rivals is "very small" compared a year ago and claims the performance is nearing the same as third-best Renault.

The Japanese manufacturer has been making steady progress throughout the season and for much of it have been building on the introduction of a Spec 3 engine which they first tested in Baku with the current version being run the Spec 3.7.

Yet the time it took to overcome the majority of issues, first seen in pre-season testing, led to partner team McLaren ending their association at the end of the season and switching to Renault, while Honda will continue with Toro Rosso.

Interestingly, Red Bull is largely positive about the switch for their junior team as it gives them the option to evaluate the progress of Honda as an alternative should the French manufacturer come up shy of expectations next season, and Hasegawa does see overhauling Renault as a possibility.

"From the beginning of the season, we have been improving the power unit - not only in terms of performance but also reliability," he told Autosport.

"Since we introduced Spec 3.5 engine, I think that level of performance is very close to the Renault. I cannot say it's better than Renault but the important thing is the reliability is much better."

Indeed, reliability has been just as big of a thorn for Renault and their customers with Red Bull advisor Helmut Marko revealing both Daniel Ricciardo and Max Verstappen will require one more engine each resulting in penalties.ore broadly Honda do think they reaching a level alongside their fellow suppliers.

More broadly Honda do think they are reaching a level alongside their fellow suppliers with their F1 chief adding: "We're not close enough, but the gap is very small compared to last year and the first year."

There is also now greater faith in the path they are on, with the emphasis now on development of their design rather than an overhaul, which led to their problems this year.

"There is no doubt in this current concept," Hasegawa claimed. "We're choosing a very similar concept to Renault, Ferrari and Mercedes.

"There is no reason we can't achieve the same level of performance with the current concept."

The carmaker had hoped to introduce the full Spec 4 unit before the end of 2017, however, an unexpected failure in Japan resulted in Fernando Alonso needing a new engine, leaving just Stoffel Vandoorne to potentially benefit at some point in the final four races.