Claire Williams says Williams is interested in retaining Felipe Massa for 2018 but hasn't ruled out the prospect of speaking to other drivers for next season.

The William deputy team principal feels both current drivers Massa and rookie Lance Stroll are delivering for the British team on its 40th year in Formula 1 after an uncertain winter having secured a deal which saw Valtteri Bottas move to Mercedes while luring Massa back out of retirement.

Massa has previously said he wouldn't necessarily aim to retire again at the end of this season, hinting at another season at with Williams, which the deputy team principal has echoed having seen a strong driver partnership develop between Massa and Stroll.

"I don't see why not [Massa to stay], he's done such a great job this year," Williams said. "We were very fortunate that he decided to come out of retirement - the shortest retirement ever - and help us out.

"We were really lucky with that and he has more than delivered this year on so many levels for us. Whether that be delivering the points haul that he has, supporting the other side of the garage and helping Lance, being a really strong team player and working with Paddy and looking at all the areas that can be improved with his level of experience that he has.

"I think as a driver, any driver needs to be motivated to continue in F1 and that's his decision whether he still has the motivation to continue, but seeing him this year, I don't doubt he has motivation at all."

Despite Williams sounding settled on an unchanged driver line-up for 2018, Williams hasn't ruled out the possibility of negotiating with other drivers later in the season if required. When quizzed whether the team would still look at other drivers even if Massa said he wants to stay she responded:

"It's only July isn't it? It's only July. It's only July, that's my answer."