Toro Rosso team boss Franz Tost believes Red Bull will be major beneficiaries from switching to Honda in 2019.

Having complained throughout the hybrid era about Renault, the Milton Keynes outfit took the risk on the Japanese manufacturer based on their progress in the first half of last year.

Now, the work is underway to make the new partnership a success, but a lingering concern remains over reliability after Honda chief Masashi Yamamoto warned penalties were inevitable this year.

"In the winter, I think that Honda has reached a very high level on the reliability level as well as on the performance side, and I don't expect that we will as many additional engine changes this year," Tost said on Monday.

"I'm very happy about this. All of the expectations I have put into them, they have delivered."

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Certainly, the initial signs were positive for Red Bull as Max Verstappen completed 128 laps on the first day of testing in Spain.

"I'm quite sure that we will close the gap to the top teams and that Red Bull Racing will be able to win races with them and we will gain a lot of advantages out of this cooperation," the Toro Rosso chief added.