Liga MX players who fail to attend Mexico's World Cup training camp starting on Wednesday will be dropped from the tournament squad, the Mexican Football Federation (FMF) said, essentially cancelling an exemption granted to players from Toluca.
Clubs had initially agreed with FMF that they would release all called-up players from May 6.
FMF later granted special permission to Toluca players to remain with their club for Wednesday's second leg of the CONCACAF Champions Cup semi-final against Los Angeles FC, in which they trail 2-1 on aggregate.
That exemption drew criticism from Amaury Vergara, owner of Guadalajara, which fields only Mexican players. Vergara later urged his club's five selected players to return for the Liga MX Clausura quarter-finals, with the team seeking to overturn a 3-1 deficit against Tigres UANL in Saturday's second leg.
"All players must report to the High Performance Centre in Mexico City," Reuters quoted the FMF as saying in a statement on Wednesday. "On the coaching staff’s instructions, any player who fails to attend the training camp today will be excluded from the World Cup."
The dispute highlighted growing tension between clubs and the national team over player availability ahead of the World Cup, with domestic and continental fixtures clashing with preparations for the tournament.
Toluca, the reigning Liga MX champions, had requested permission since the start of the season to keep players available. After the FMF statement, Toluca said they would release Jesus Gallardo and Alexis Vega to join the national team.
"Toluca acted at all times in compliance with FMF regulations," the club said in a statement. "A specific authorization was requested in advance ... and validation was granted by Liga MX and the FMF.
"The club will release their players and do without them for tonight’s crucial match in the second leg of the CONCACAF Champions League semi-final."
Mexico, co-hosts of the World Cup alongside the US and Canada, will complete their preparations with friendlies against Ghana on May 22, Australia on May 30 and Serbia on June 4, before opening the tournament against South Africa in Group A on June 11.