Paris Saint-Germain will refuse to comply with an order by the league to pay Kylian Mbappe 55 million euros ($59.5 million) in back pay, a source close to the case told AFP on Friday.
A French league appeals committee has attempted to mediate in the increasingly bitter row between Real Madrid forward Mbappe and the club he left this year.
Mbappe has demanded the figure which he says is made up of the final three months of his salary plus several bonuses.
But Qatar-owned PSG argue that the 25-year-old had agreed to waive the sum in August 2023.
With PSG flatly refusing to abide by the league's order to pay their former player the money, the case looks set to drag on.
AFP has contacted Mbappe's spokespeople for comment.
According to reports in Sweden, Mbappe is the subject of a rape investigation following a visit to Stockholm earlier this month, although Swedish authorities have not named him.
Mbappe trained in the Spanish capital on Friday in preparation for his first El Clasico -- the clash with Barcelona that is traditionally the Spanish league's most eagerly-awaited match of the season -- since he joined the European champions in June.
Real host Barca at the Santiago Bernabeu on Saturday.
Coach Carlo Ancelotti said Friday the star forward was preparing well.
"He seems very calm in the way he is getting ready, he has confidence in his own ability, and I think he will give us a lot tomorrow, as always," Ancelotti said.
A World Cup winner as a teenager in 2018, Mbappe scored a club record 256 goals for PSG after joining the Qatar-owned club from Monaco on an initial loan deal in 2017.
He eventually moved to PSG in a 180-million-euro deal -- all at the age of 18.
Mbappe helped PSG to six Ligue 1 titles and steered them to the 2020 Champions League final, but they lost to Bayern Munich.
He scored a hat-trick in the World Cup final against Argentina in Qatar in 2022 but still finished on the losing side as Lionel Messi's Argentina won on penalties.