Barcelona believe they have lost ground to Juventus, Paris Saint-Germain and Bayern Munich in the race to sign Ajax defender Matthijs de Ligt, sources have told ESPN FC.

Sources close to the negotiations said that the "optimism" which Barca maintained a few weeks ago has decreased due to the renewed interest of some of Europe's biggest clubs and the excessive demands from De Ligt and his agent, Mino Raiola.

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"We can't move any more on what we've offered," a Barcelona source told ESPN FC. "One of the things that could benefit us is the player's desire to come here, but we will see if that really is what he wants in the end."

Barcelona have been leading the chase for the in-demand centre-back for weeks. They already have an agreement in principle with Ajax to sign him for a similar figure to what they will pay for Frenkie de Jong -- €75 million plus add-ons.

But they have still not managed to strike a deal with De Ligt and Raiola, which has allowed Juve, PSG and Bayern to re-open negotiations and attempt to better the offer made by Barca, who are beginning to tire of the player's elevated financial demands.

The main problem facing Barca is Raiola's attempt to take advantage of the interest from elsewhere and De Ligt's excellent end to the season to push for a salary which the Catalan club are not prepared to pay.

De Ligt helped Ajax win a domestic double and reach the Champions League semifinal -- and that is being used as a reason to backtrack on an agreement struck with Barcelona in March and ask for more money, as revealed by ESPN FC earlier this month.

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Barca are unable to meet those new demands and sources have said the club will not budge another inch from the last offer they made. They hope other factors will play in their favour, such as the player's will to move to Camp Nou, the signing of De Jong and the chance to play with Lionel Messi.

Juve's sporting director Fabio Paratici said two weeks ago that De Ligt "will sign for Barcelona" following a conversation with his Ajax counterpart, Marc Overmars. But talks between Barca and De Ligt have hit a snag and sources have suggested Juve and PSG may now be better placed to land the defender.

Barca have worked on the deal for months. After announcing the signing of De Jong in January, president Josep Maria Bartomeu made the decision to push hard for De Ligt, even though he wasn't a priority for the club at the time. Given the good relationship with Ajax, they were able to loosely agree the framework of a fee with the belief they would be able to convince the player to join.

Bartomeu himself said in an interview with ESPN FC in April that he knew what would happen with De Ligt this summer, but he could not say. Despite that, things have changed in recent weeks and the situation is not so rosy for the Blaugrana anymore.

De Ligt, before facing Juve in the Champions League quarterfinal, said that his future would be decided by Raiola. Few believed him at the time but there is now a realisation of just how much power the agent has over his client.

"Raiola is very good at what he does -- he is spectacular at seducing players and [De Ligt] is completely committed to him," a source told ESPN FC.

PSG declined to comment when asked by ESPN FC, while Raiola is unavailable due to a suspension.