Reports on Thursday morning have suggested the Portugal winger could be out for up to six weeks.

But United, who issued a statement on Wednesday night about Ronaldo's injury, are baffled by those comments.

A club spokesman reiterated: "Procedures are in place to seek specialist advice, in order to finalise the treatment plan as soon as possible."

On Wednesday night they had stated: "Manchester United medical staff met with the medical team from the Portuguese FA and Cristiano Ronaldo in Lisbon today (Wednesday) regarding the ongoing treatment of his injured right ankle.

"As a result, further specialist advice is being sought and an announcement will be made on any action in due course."

Should it be decided an operation is required, it could have a major impact over the Madeira-born winger's fitness for the start of the new season.

That in turn may determine how far Real Madrid are willing to push their attempts to lure him away from Old Trafford.

Ronaldo is not due back in England for another fortnight and manager Sir Alex Ferguson is yet to speak to him about the large number of statements from Madrid - which went unchecked by the player - during Euro 2008.

Eventually, United grew so sick of Real's advances that they reported the matter to FIFA, although the world governing body subsequently rejected it.

Ronaldo refused to comment on his future when he returned to Portugal after a break in Italy.

"I can only say that I will spend the period of my recovery in my house in Sintra, but regarding my future I cannot say anything," Ronaldo said in Portuguese newspaper A Bola.