FIFA president Sepp Blatter has apologized to Real Madrid and Cristiano Ronaldo for a joke he made about the star player's hair on Tuesday.

Blatter tried to downplay an incident that had pitted the sport's most powerful executive with its richest club and one of its biggest stars.

Blatter had told an audience at Oxford University that Ronaldo "is like a commander on the field of play" before strutting around the stage to the laughs of the students in attendance.

Madrid coach Carlo Ancelotti said early on Tuesday that club president Florentino Perez had sent a letter to Blatter asking him to "rectify what I consider a lack of respect for a serious and professional player."

Blatter asked both Ronaldo and his club for forgiveness, sending a letter back to Perez, which Madrid posted on its website.

"I want to clarify that for me Cristiano Ronaldo is at the same level as Messi and that they are both outstanding players, each in their own way," Blatter said in the letter.

Blatter said he was "sorry that this situation produced in a university event hurt as much and I apologize for it. It was never my intention to embarrass or disrespect Real Madrid CF, or one of their players or their fans..."

While slighting Ronaldo during the public event, Blatter said he preferred Messi, the Argentina forward who has won FIFA's World Player of the Year award for the past four years.

Then, while comparing Messi and Ronaldo, Blatter made a joke about Ronaldo's hair.

"They don't have the same attitude and that gives life to football. One has more expenses for the hairdresser than the other but that doesn't matter," Blatter said.