Valtteri Bottas' much speculated move to Mercedes could be announced this week as Claire Williams confirmed Williams Martini Racing won't stand in a way of his deal with the title winning team.

Bottas emerged as the leading candidate to replace Nico Rosberg in the Mercedes line-up when the reigning champion announced his shock retirement in December only days after winning the world championship for the first time.

The Finn was originally set to stay with Williams - with whom he made his F1 debut in 2013 - this season but a deal to take him to Mercedes alongside Lewis Hamilton is understood to have been agreed and could be announced later this week.

Though Williams reportedly spurned Mercedes' initial advances for Bottas with a deal thought to include a reduction on their engine bill and the offer of Pascal Wehrlein to replace him, Williams admits there is little desire to stand in the way of his 'great opportunity'.

"It has been dragging on and I think everyone wants to know, probably more who is going to be Lewis' team-mate next year, and of course whenever Nico made his announcement we knew the call was probably going to come from Toto," Williams told Sky Sports News.

"It is a great opportunity for Valtteri and he has given a lot to Williams. We've always said if we can make this happen on terms that are positive for Williams then it is probably the right thing to do.

"No-one needs or wants a driver in your team that really wants to be somewhere else. It is not nice either to stop a driver who has such a great opportunity, particularly at this point of Valtteri's career, but it has to work for Williams and that is what we've been working hard on over the past six weeks.

"We are nearly there, we are at the tail end of it and hopefully we'll be able to make an announcement this coming week.

"But it has to be right for Williams, whatever we do will always be the right decision for Williams no matter what other people's opinions might be."

Despite the offer of Wehrlein, Williams is set to call upon Felipe Massa to replace Bottas and partner rookie Lance Stroll. The Brazilian, who raced with Williams between 2014 and 2016 originally planned to retire from the sport after losing his seat to Stroll but is now poised to return.