Real Madrid superstar Cristiano Ronaldo denied that he is insulting FC Barcelona rival Lionel Messi behind close doors, contrary to what Spanish football analyst Guillem Balague wrote in his new book.

In his book titled "Messi" that appeared on the Guardian, Balague wrote that Ronaldo is calling Messi obscene nicknames behind the media every time the Portugal international will be matched up against his Argentine counterpart.

"Ronaldo, perhaps as a symptom of the immaturity that marks so many footballers, thinks it necessary to put on a brave face in front of his team-mates, not be scared of Messi and to rise to the challenge. All very macho; all very false," Balague wrote. "And that is why, according to some Real Madrid players, CR7 has a nickname for him: 'm-----f-----.'''

Balague also added that Real Madrid players also have insulting jokes about Messi with some players labeling the Argentine superstar as Ronaldo's dog or puppet.

But when he heard about the news, Ronaldo posted a statement on his official Facebook page, denying the allegation and reiterating that he respects Messi. The Real Madrid icon also added that he will take legal actions against Balague for his allegations.

"News is circulating that I allegedly made offending remarks regarding Lionel Messi," Ronaldo posted. "This is absolutely false and I have assured my lawyer takes action to sue those responsible. I have the utmost respect for all my professional colleagues, and Messi is obviously no exception."

Ronaldo and Messi have faced each other on the pitch numerous times - both in club and international competitions. The never-ending comparison between them will heat up once again as Argentina and Portugal are scheduled to collide in a friendly match next week.

The two football superstars also went toe-to-toe against each other for the FIFA Ballon d'Or award over the past several years. While they are casual in front of the media, Balague pointed out that both Messi and Ronaldo dislike each other.

"Messi and Ronaldo are not friends but they are polite to one another in public; anything else, those who are close to them insist, is all media-generated," Balague added. "Messi admires Cristiano's shooting and heading ability but is tired of comparisons between the two of them. He understands that Ronaldo is not comfortable about it either."