Williams reserve driver Robert Kubica has admitted he may not achieve his final goal of making a full-time return to the Formula 1 grid.

The Pole has been looking for opportunities to do so for over a year, completing a series of tests with Renault before targeting Williams in the latter half of last season.

Ultimately, it ended with the third driver role he currently has at the Grove-based team but hopes for that final step appear mixed.

“For me, it is more speculation than emotion,” Kubica told Poland’s Przeglad Sportowy. “A lot happened in [the] F1 [driver market] in August, but for me it’s not like a lot of doors suddenly opened or closed.”

The 33-year-old has completed several Friday practice appearances with Williams and has even been linked to Toro Rosso for 2019 but Kubica knows nothing is guaranteed.

“What I was trying to do was drive an F1 car. Currently, the regulations are not favourable because there is almost no testing," he said.

“So my priority was to sit behind the wheel, but of course by signing a contract you have to be professional and in case something happens, get in the car and do your job.

“But the fact that I could get into the car does not automatically mean that I will be able to do all the races.

“On the one hand it would be the accomplishment of a dream, but on the other, it may not have the happy end that I want.”

With Lance Stroll's exit at Williams looming, Kubica had been considered a natural replacement, although the influence of sponsorship backing could again thwart that possibility.

As a Mercedes customer, the plight of Esteban Ocon is another factor with the highly-rated Frenchman seeking to remain on the grid.

“If I was him, I would not be pushing too much for it,” Kubica said of Ocon moving to Williams. “But I just do my own thing.”