Valtteri Bottas admits he expected more from Williams F1 in 2015

At this point in 2014, Bottas had enjoyed a run of four podium finishes in five grands prix.

This year he has only stepped onto the podium once - in Canada - with team-mate Felipe Massa matching that third place in the following race in Austria.

Hopes of building on last year's performances have not materialised as the car has struggled on occasion, notably in damp or wet conditions.

But Bottas, poised to retain his seat with the team for 2016 now speculation surrounding a move to Ferrari has disappeared with Kimi Raikkonen remaining with the Scuderia, firmly believes progress can be made for the remainder of this season and into next year.

"I think Williams is a great team to be with, and I'm confident they can be up there again in 2016," said Bottas in his blog on the Williams website.

"There's no reason why Williams shouldn't be able to be fight with Ferrari and Red Bull.

"I do admit we expected more from this year's car, particularly in the first part of the season.

"If you compare it with 2014, then we had a few more podiums at this time of the year than we have now.

"Having said that we are still capable of improving and getting closer to Ferrari so I will be looking to secure more podiums in the second half of the season."

Bottas qualified third at last weekend's Belgian GP, but could only finish ninth after a bungled pitstop when a medium tyre was fitted to his right-rear wheel amid a set of softs, leading to a drivethrough penalty.

"A lot of work is going to go into understanding how the tyre mishap happened because we need to fix the procedures and make sure such a problem never occurs again," he said.

"We'll learn from it and I'm sure this will never be repeated."