Lewis Hamilton is poised for a shock move to Ferrari for the 2025 season.
Several sources say claims of links between the seven-time champion and Ferrari should be taken seriously. A deal could be announced as early as Thursday.
Ferrari want Hamilton to join Charles Leclerc for the 2025 season.
The 39-year-old signed a new two-year deal with Mercedes for 2024 and 2025 last summer but it seems he can leave after one season, should he choose.
The possibility of Hamilton moving to Ferrari in 2025 was reported in the Italian and Spanish media on Thursday.
BBC Sport has since verified the fact that it is a serious possibility.
There have been intermittent rumours of Hamilton moving to Ferrari for years. Until now, these have turned out to have little substance, but a number of sources say this is different.
Ferrari and Mercedes have refused to comment.
Sources have told BBC Sport that all Mercedes team members have been called to a team briefing with boss Toto Wolff and technical director James Allison at 14:00 GMT on Thursday. This is likely to be to announce Hamilton is leaving.
Assuming it happens, the move will send shockwaves through F1 - similar to those Hamilton caused when he chose to leave McLaren for Mercedes for the 2013 season.
At the time, many questioned Hamilton's decision, but it turned out to be remarkably prescient - he and the team dominated F1 from the 2014 season, making the Briton the most successful driver in F1 history.
To the outside world, this will appear a similar gamble, and many will assume that Hamilton has lost confidence in Mercedes' ability to deliver him the eighth world title he so craves after the controversy of Abu Dhabi 2021.
The lure of Ferrari, the sport's most historic and evocative team, is strong for many drivers. Until now, Hamilton seemed to be immune to it - he has said on several occasions that he wanted to spend the rest of his life with Mercedes, and the pair have a number of projects together, especially on diversity and racial equality.
But it seems the chance to spend the final years of his career driving for Ferrari may be too good to turn down - it is something Hamilton's boyhood idol Ayrton Senna was also planning to do before he was killed in a crash while driving for Williams in the 1994 San Marino Grand Prix.
At the end of last season, Hamilton was sounding equivocal about his belief in Mercedes' ability to recover from two difficult seasons and challenge Red Bull.
In an interview with BBC Sport and other selected outlets at the final race of the season in Abu Dhabi, he said: "I do believe we have a North Star now. Which I don't think we've had for two years. But still getting there is not a straight line. I think we understand the car so much better.
"They have developed great tools in the background. So naturally, I'm hopeful, but I'm not going to hold my breath."
Should Hamilton's move be confirmed, it would explode the F1 driver market.
Mercedes would be looking for a replacement for Hamilton at the end of the season, Ferrari's Carlos Sainz would be looking for a new job.
And other than Fernando Alonso, whose Aston Martin contract expires this season, none of the recognised top drivers would be available to join Mercedes alongside George Russell.
Max Verstappen is contracted to Red Bull until 2027, Leclerc is committed to Ferrari and Lando Norris has also just signed a new deal at McLaren.
Ferrari have also had a difficult few seasons, and the two teams were locked in a battle for second in the constructors' championship last year, which Mercedes narrowly won despite the Ferrari being the faster car by the end of the season.
BBC