Sponsored by Martini, Williams are reportedly waiting for Lance Stroll's 18th birthday to confirm him as Valtteri Bottas' 2017 team-mate.
According to a report on Motorsport.com, Williams are pressing on with plans to sign Stroll for next season following his title success in the European Formula 3 Championship.
The team, though, are unlikely to make the announcement until Stroll is 18 because of their title sponsor, Martini.
At just 17 years of age Williams are concerned that there could be "complications" with his age given that Martini is an alcohol brand.
As such the team will wait until he turns 18 on 29 October, which is the Saturday of the Mexican GP weekend.
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