Toro Rosso driver Pierre Gasly is feeling positive about Honda and what he described as their "big, big" plan for engine development in 2018.

The Japanese manufacturer, who switched to the junior Red Bull team from McLaren for this season, had appeared to make significant gains in testing as the STR13 ran very reliably in Barcelona.

When the action got serious in Australia though, the performance remained lacking, with Brendon Hartley last of the classified finishers and Gasly retiring due to an MGU-H problem in the race.

At the time, the Frenchman admitted it was a "pain in the ass" but, looking forward, is encouraged by what Honda is doing.

"On their side they are pushing flat out because they really want to show everyone they can do proper engines," he was quoted by Autosport. "In terms of the development already we can see some really positive progress.

"We are pushing to have as many upgrades as we can, but of course we know we only have three engines so we need to see exactly when is the best time to bring them."

The performance in Australia could well have knocked some confidence within those at Red Bull, with the senior team watching their results closely as they consider their engine options for 2019.

What is most frustrating for Honda though, Gasly admits, is the goalposts are always shifting.

"It's all going well, but we also need to give them [Honda] time because it's F1 - they are all pushing: Mercedes, Ferrari, Renault, they are all pushing and improving all the time.

"For sure they cannot recover everything in only three or four months, but in terms of medium to long-term collaboration I think they have a big, big plan ahead, and at the moment they are doing the right things and really pushing hard."

What is worrying, however, is the former GP2 champion sees high downforce circuits like Melbourne as Toro Rosso's best chance for results.

"Haas is way too fast; Renault as well - we're fighting with the Williams and Force India," he said. "We know our car is really good in low-speed, so there will be tracks which suit our car a bit better.

"We need to wait and see the other races, but we have potential to fight."