Sepp Blatter has said Real Madrid and Atletico Madrid will face "similar sanctions" to Barcelona if they are found guilty of infringing FIFA rules on youth players.
Barca were banned from registering new signings for two consecutive transfer windows after being found guilty of repeatedly breaching rules relating to the signing of young players.
It was widely reported in April that the two Madrid clubs were also set to face one-year transfer bans for irregularities in signing youth players but Real quickly issued a statement to dismiss the claims.
The following month, Real issued a fresh denial after AS reported that the club had partnered with a private company, Soxna, in a deal to bring 25 Chinese youngsters under the age of 14 to live and develop as footballers in Spain.
Blatter, who is currently fighting his suspension as FIFA president, has now given an interview to Catalan newspaper El Mundo Deportivo in which he said he expected Real and Atletico to be treated in the same manner as Barca.
"These are closed investigations, and I can't even set foot inside FIFA, but if Barca faced sanctions for breaking FIFA rules and the two Madrid clubs committed identical infractions, then it's normal practice that they would face similar sanctions," he said, in quotes translated by AS.
Barcelona president Josep Maria Bartomeu said in January that he did not wish to see Real punished and that FIFA's transfer rules should instead be changed.
However, Blatter said: "Maybe Barcelona made a mistake starting this war against FIFA. It would have been better to open a dialogue, a path that always works better in football."