Fernando Alonso believes McLaren will discover whether their consistent claims of having a chassis capable of fighting at the front of the Formula 1 grid are true or false when they switch to Renault engines from 2018.

The Spaniard is still not confirmed as a driver for the British team next season, although is widely expected to sign a new extension to his contract which expires at the end of the year, and he is fuelling that likelihood by talking up McLaren's chances since confirming the change in supplier.

Now with a power unit that has won races in back of a Red Bull, and the Milton Keynes outfit as an excellent bar at which to aim at, the double world champion believes the onus is now on the Woking team to prove Honda was the sole reason for their lack of competitiveness.

"Next year will be a good test," Alonso told Sky Sports F1. "The same engine as Red Bull will be the truth to see whether the chassis is good or not.

"For the last three years, we have been the only team with the Honda engine so it's been hard to compare. But the engineers do simulations on everything and we believe we have a good car."

Racing director Eric Boullier echoed his driver's claim, telling the official F1 website: "Today we know that we have a decent chassis, which would allow us to be in the top three again with an equal level engine."

The Frenchman also revealed, however, that the talks with Renault and the deal that had to be agreed with Red Bull for them to allow Honda to continue with Toro Rosso, had led to a minor delay in 2018 preparation.

"Two weeks is recoverable, it won't be any compromise next year," said Boullier. "Of course, we don't have the same experience as some of the customers, so we have to discover the package but, I think we can trust our engineers to do a very good job and two weeks are recoverable."

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The end of the Honda partnership has led to the Japanese manufacturer altering their approach in terms of engine development for the remainder of this season, after expediating the introduction of new updates and building towards the 'Spec 4' engine since Belgium.

Instead, from now, the supplier will only fully implement the full upgrade when they feel it is ready to do so.

“One of the points is we want to minimise the engine upgrades for the rest of the season, but that is because we’d like to get the maximum results within this year,” said Honda’s F1 chief Yusuke Hasegawa.

“Previously we just prioritised the performance improvement because any improvement is continuing for next year, so we didn’t need to hesitate to introduce upgrades, but now we won’t be working together with Stoffel and Fernando next year, that means we want to concentrate on this year’s results for McLaren.

“I prefer to score more points this year, I’d like to contribute to this team, most of all."

Considering when that one major upgrade, which would then result in grid penalties, would come, he added: “That could maybe be in Malaysia, Suzuka or the US.

“From that point of view we will try and avoid the penalty in Suzuka obviously, and the US could be a very good potential circuit for us based on the last years' results. Malaysia could be a chance but it’s too soon to say. It will be difficult so I cannot confirm.”