Williams convinced Massa to come out of retirement to partner Lance Stroll this season, after Valtteri Bottas moved to Mercedes to replace world champion Nico Rosberg.

The Brazilian agreed a one-year deal and though he is in talks with Williams over a fifth season with the outfit, a firm decision has yet to be made.

Massa has said he needs Williams to show it wants to keep him and that he does not want to be seen as a last resort when no other suitable drivers are available.

When asked if it was Williams or nothing next year, he said: "I think so. Or maybe something happens, a guy like [Nico] Rosberg decides to retire. But I don't think it will happen."

Massa said he had enquired elsewhere for a seat but could not find a suitable project.

"I look but maybe teams that I looked, maybe they had a different direction in terms of drivers," he said. "Now no [talks with other teams]. Now I check if I stay or not. "

Massa, who has previously said he will head to Formula E if he leaves F1, added he has yet to decide what he wants to do.

"I'm still thinking, I'm still talking with the team, to see if they want me or not. I need to be sure maybe I can have a better year."

Motorsport.com understands Williams has slimmed its shortlist for the seat alongside Stroll down to Massa, Robert Kubica and current reserve driver Paul di Resta, who delivered a strong performance when standing in for Massa in Hungary.

Sources suggest Williams is in no rush to make a final decision given it is in a strong position amid a lack of vacancies elsewhere.

It is also planning to give Kubica some mileage in a 2014-spec Williams in a private test.