Cristiano Ronaldo [Images] believes FIFA president Sepp Blatter was right to compare long-term contracts between soccer players and their clubs as a form of "modern slavery".

Reacting to Blatter's comments, wherein the head of football's world body said the Manchester United [Images] and Portugal star should be allowed to join Spanish giants Real Madrid [Images] if he wants to, Ronaldo said, "I completely agree with the FIFA president. He is correct, but I do not want to say more."

• Long-term deals like slavery: Blatter

Ronaldo, who has already spent more than three years at English champions United, is currently recuperating in Portugal after undergoing surgery on his right ankle. He scored 42 goals for Man United last season, powering them to them to the title in the English Premier League and Champions League.

Asked specifically about Manchester United's efforts to prevent Ronaldo leaving to join Real, Blatter said the English side should let him go.

"If the player wants to play somewhere else, then a solution should be found," he said. "Because if he stays in a club where he does not feel comfortable to play then it's no good for the player and for the club."