Williams looks set to announce Robert Kubica as its second driver for 2019 this weekend in Abu Dhabi.
Journalist Cezary Gutowski, who writes for the Polish publication PrzeglÄ d Sportowy, said the British team is planning to make the news public on Thursday.
The identity of George Russell's teammate looks likely to be Polish driver Kubica.
The current occupant of the seat, Russian Sergey Sirotkin, admitted he is nervous.
"Right now, sitting here, I want clarity," he told the Russian publication Sport-Express.
"It is very unpleasant to read the latest news. But in Abu Dhabi I will get behind the wheel and all of the problems disappear."
Sirotkin said he does not want to take a step back into a testing role.
"Of course I'm not ready for that," he said. "I have said repeatedly that I invested much more in this season than people see, and the last thing I want is for the results of my work to go to someone else.
"It is clear that this year we worked for the future, with the results coming next season. If I lose what I worked on, it will be a big disappointment," Sirotkin added.
33-year-old Kubica, the Williams reserve this year, has not raced in F1 since almost severing his forearm in a 2011 rally crash.
His father Artur is hopeful.
"Everything seems to indicate that Robert will come back to racing," he said.
