Kylian Mbappe told Paris Saint-Germain on Monday that he would not be taking up an option to extend his contract until 2025, raising the spectre of him following Lionel Messi out of the club this summer.
The 24-year-old France striker's current deal expires at the end of next season, with the option of another year.
If he does not sign, the French champions risk losing him for nothing in a year's time -- so they could now sell him this summer rather than miss out on a windfall for one of the world's best players.
Mbappe's decision not to renew, announced in a letter to the club and revealed by the French sports daily L'Equipe, is a fresh blow to PSG following the loss of Messi to Inter Miami.
There had been a deadline of 23 July, 2023, for Mbappe to decide.
Mbappe's move comes a little over a year since he snubbed Real Madrid by signing a surprise extension to his contract to remain at the Parc des Princes.
Real would again be chief among his suitors.
Mbappe's entourage did not respond immediately when asked late Monday evening.
The striker's departure for free at the end of his current contract, in the summer of 2024, would prove catastrophic for PSG.
In addition to the void left in the team, the club would also be deprived of the millions of euros a transfer would earn.
The future of Brazilian fellow star striker Neymar, under contract until 2025, also appears vague ahead of what is shaping up to be a summer of upheaval in the French capital.
Growing doubts over future
Mbappe joined PSG on a season-long loan from Monaco in August 2017 that turned into a permanent deal worth 180 million euros ($194 million).
He helped France to World Cup glory as a teenager in 2018 and has established himself as arguably the leading forward on the global stage.
Mbappe also scored a hat-trick in France's 2022 World Cup final defeat to Messi's Argentina and helped Paris Saint-Germain win a record 11th French title.
But Mbappe hinted last month that he could leave in 2024.
"I said that next year I will play at PSG. I still have a year of contract so I will honour my contract," he said when asked about his future at an awards ceremony where he was voted the Ligue 1 player of the season for the fourth successive time.
At Clairefontaine, where France are preparing for their next Euro qualifying matches, the striker appeared relaxed on Monday.
Smiling and joking with coach Didier Deschamps and fellow attacker Antoine Griezmann, he participated in afternoon training and signed dozens of autographs for spectators.
The announcement of Mbappe's intentions to PSG are yet another annoyance for the club's Qatari owners following a difficult season on and off the pitch, despite winning the French title.
After another failure in the Champions League, the club are working to find a successor to coach Christophe Galtier.
The season was widely seen as a disappointment after PSG were dumped out of the Champions League by Bayern Munich in the last 16 and from the French Cup at the same stage.
As for Neymar, the Brazilian's fitness has regularly been a concern for PSG, ever since he signed from Barcelona for a world-record fee of 222 million euros in 2017.
He has scored 118 goals in 173 games for PSG, but has missed more than 100 games due either to injury or suspension.