Honda's power unit is now at the level of performance anticipated in the pre-season testing according to the head of their Formula 1 program Yusuke Hasegawa.

The Japanese manufacturer has been playing catch up throughout 2017 as the heavily revised engine they introduced for this year suffered several major flaws including having to relocate the oil tank and vibrations as the revs increased.

Now it seems they have been largely sorted out and the recently introduced Spec 3 engine has allowed partner McLaren to be a little more competitive, including a double points result at the last race in Hungary.

The problem for Hasegawa is, while the rate of development is reasonably good, it has cost both team and supplier much of the season.

"It is difficult for me to say it is satisfying," Hasegawa told Racer. "Maybe the current level of performance is what we had to achieve at the beginning of the season. So for me, I'm thinking, 'At last we can achieve the level of performance we should have been at in Barcelona'.

"So it took around five months. From a normal technical development common sense point of view, to catch up that level in five months, we have to be proud of that. However, to match the F1 calendar, it is too late. So I am half relieved and half very disappointed that we could not achieve this level at the beginning of the season."

The difficulties have had consequences with McLaren looking at Renault as an alternative with a decision likely made next month. While Sauber, who had signed to become the first customer team of Honda, cancelled that deal in favour of remaining with Ferrari.

Commenting on the McLaren situation, with it appearing the two parties will continue, Hasegawa said: "Actually we are frequently talking and we still have very strong communication. So we don't need to make any special meetings with them."

Recent reports have also indicated Toro Rosso could be eyeing a supply deal perhaps from next year but signs point to 2019.