Contract issues related to Robert Kubica's insurance claims are likely the reason behind Williams' delay in announcing a deal with the Pole.
Following claims from German and French media that Kubica had signed a two-year deal with the Grove-based outfit, the British squad dispelled the comments, insisting no news on its 2018 driver line-up would be released in Abu Dhabi next weekend.
However, according to Motorsport Magazine's Mark Hughes, a deal has apparently been agreed, but will only be inked when complicated personal paperwork linked to Kubica is completed.
"Although the 2018 deal has still to be confirmed, our understanding is that he will, in fact, be racing for the team next year, pending the expected resolution of contract issues," Hughes wrote.
"The delay is believed to be about the structure of his payments, and this is almost certainly linked to the fact that an insurance pay-out for the ending of his career will now have to be paid back."
In the interim, Williams has confirmed Kubica's presence at next week's post-race Pirelli test at Yas Marina, where the Pole will run with a 2017-spec car alongside Lance Stroll and Sergey Sirotkin.