It will take Williams years to return to the top four places in the constructors' world championship.

That is the frank admission of new team boss James Vowles, who switched from Mercedes over the winter to replace the ousted Jost Capito.

"It's about what I expected," Vowles, 43, told France's Auto Hebdo. "It may even be a little more difficult than that."

Williams has been out of F1's top four teams since 2015, but the last win dates all the way back to 2012 - and Jacques Villeneuve's 1997 triumph was the most recent of 9 constructors' and 7 drivers' titles in total.

"Over the past 15 years, the team has gone through tremendous hardships, financial and otherwise, and they have survived it all," Vowles said.

"But it was only survival, compared to other teams that had the financial means. That is why there are major differences between our current situation and the one we must have in the future.

"It is incredibly difficult to get into the top three," Vowles continued. "These teams have resources that are beyond your dreams, but they also have the experience and the best people on the grid."

A return to the top four for Williams, therefore, is a long-term goal according to Vowles.

"I think a realistic step for this organisation is, first and foremost, to make sure that each year we move forward and that we don't stay in the same place. That must be dream number one," he said.

"Dream number two is to set a reasonable period in the future, and I mean years, where we will start to break through for sixth, then fifth, then fourth."