Robert Kubica's father insists his son is still in contention for Williams' coveted second seat alongside Lance Stroll for 2018.
Amid rumors the Grove-based outfit has now set its sights on Sergey Sirotkin, with an announcement coming possibly as early as today, Arthur Kubica says they are pushing hard for the drive.
"We're still fighting to get Robert into Williams," said the father of the 32-year-old driver, speaking to Poland's Sportowe Fakty.
"We hope that it is a good decision for us. And if it is not made before Christmas, it means that at least the people at Williams are taking time to think.
"We are taking steps to convince them to believe in Robert," he added.
Williams was impressed with Sirotkin's performance at the recent post-season Abu Dhabi test in which Kubica also took part.
But the 22-year-old Russian also enjoys a lavish sponsorship support package rumored to be worth at least 15 million euros, courtesy of his long-time personal backers SMP, and which could prove to be the ultimate deal breaker.
"Of course it is about what the driver will bring to the team," admitted Kubica senior.
"Sometimes, skills, experience and the potential of the driver are decisive, at others only the money counts," admitted Kubica senior.
Sportowe Fakty also claimed Kubica visited Williams' Grove factory on Thursday.