Real Madrid are in talks with Paris Saint-Germain over the signing of Neymar, according to Sky Sports sources.
The Brazil forward is understood to have told PSG he wants to leave the club this summer, having joined from Barcelona in 2017, but the French champions have yet to receive a formal offer.
PSG are unlikely to sanction a sale unless they are able to recoup the £200m they spent on Neymar.
Barcelona vice-president, Jordi Cardoner, said a move to re-sign the 27-year-old can be "ruled out" at this time and that opens the door to a controversial switch to their arch-rivals.
Neymar enjoyed four trophy-laden years in La Liga with Barca, winning two league titles, a Champions League and FIFA Club World Cup.
He also won back-to-back Ligue 1 titles with PSG, scoring 51 goals in 56 appearances.
Real Madrid have been busy in this transfer window after finishing 19 points behind champions Barcelona last season.
Eden Hazard, Luka Jovic, Eder Militao, Ferland Mendy and Rodrygo have all moved to the Bernabeu while Real also had a bid of £27.6m plus James Rodriguez for Paul Pogba rejected.