Williams, 22, has been heavily linked with a summer move to the Catalan giants, who remain under close scrutiny over their financial compliance. The Spain international has a 58 million euros release clause and is under contract at Athletic until June 2027.
In a statement issued Thursday, the Basque club confirmed that a meeting had taken place in Madrid this week with LaLiga officials - including league president Javier Tebas - to discuss Barcelona's eligibility to operate in the transfer market.
"The meeting was held in response to a request made by Athletic concerning compliance with financial fair play rules," the club said. "Among the issues discussed was Barcelona's ability to sign players. Athletic have a legitimate interest in accessing relevant information about this, given that Barcelona's director of football, Deco, publicly acknowledged their intent to sign a player from our first team."
Barca sporting director Deco told media last weekend that Williams had shown a "strong desire" to join the reigning LaLiga champions. On Wednesday, club president Joan Laporta expressed confidence that Barca will be able to both sign and register two arrivals: Espanyol goalkeeper Joan García, who arrived for 25 million euros, and Williams.
While Athletic did not reveal the outcome of the meeting, they emphasized their intent to ensure that all clubs adhere to the financial rules collectively agreed upon by LaLiga members.
"Seeking clarification about these matters helps to ensure that the rules of the competition are followed properly. Athletic will vigorously defend its interests in accordance with the financial fair play regulations," the statement continued.
Laporta, for his part, appeared dismissive of Athletic's actions, questioning their motivations.
"I don't understand Athletic's reaction," he told reporters. "With all due respect, everyone should worry about their own business. We've taken all the necessary steps to sign players normally."
Tensions between Barca and other Spanish clubs have simmered in recent transfer windows. Earlier this year, several clubs objected when Spain's sports ministry approved Barca's registration of Dani Olmo and Pau Víctor, despite LaLiga's claim that the club lacked the financial margin to do so.
Tebas, who has frequently sparred with Laporta over Barcelona's finances, reiterated this week that the club continues to exceed its wage and spending limits, and must either raise capital or make significant reductions before adding new players to the squad.
Williams, one of LaLiga's breakout stars, has already informed Athletic of his desire to leave, a source confirmed to ESPN. His agent, Felix Tainta, recently communicated the player's intentions to the club, although no preferred destination was specified.
Barcelona attempted to sign Williams last summer, but the deal collapsed due to concerns over their ability to register him. They ultimately turned to Olmo instead. Williams has made 167 appearances for Athletic since debuting in 2021, forming a key part of the squad alongside his older brother Inaki.
As it stands, Barcelona's interest remains strong - but their ability to act on it may yet depend on LaLiga's interpretation of the financial rulebook.
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Barcelona's sporting director, Deco, has made it clear that any potential move for Athletic Bilbao's Nico Williams would be driven by the winger's fit within the club's sporting project, not his friendship with Lamine Yamal.
