Williams have told Jenson Button they will not "wait around" for him or McLaren to make a decision on 2017 before deciding its own line up for next year.
Button, whose McLaren contract expires at the end of this year, has been linked with a return to Williams, where his F1 career started in 2000. McLaren is delaying a decision between Button and the highly-rated Stoffel Vandoorne, who scored a point on his debut in Bahrain while deputising for the injured Fernando Alonso, until after the summer break.
Williams deputy team boss Claire Williams has admitted Button is very much on the team's wish list for next year but is refusing to let his situation at McLaren dictate Williams' own future.