Ronaldo, who has not played since aggravating the problem in Portugal's 3-0 win over Hungary on October 10, was due to return to action around now.
But Real said tests conducted on Wednesday by a doctor in Amsterdam who treated the same ankle last year had confirmed he would require another two weeks of treatment.
He would return to consult the doctor, Niek van Dijk, in Amsterdam in 15 days, they added on their website.
Ronaldo is set to miss Saturday's trip to city rivals Atletico Madrid as well as their attempt to overturn a 4-0 deficit against third-tier side Alcorcon in Tuesday's King's Cup last 32 second leg at the Bernabeu.
The Portuguese Football Federation on Thursday played down a report in Spanish sports daily Marca that said the injury will take at least another month to heal, forcing Ronaldo out of the two-legged World Cup playoff against Bosnia.
He could be sidelined for three months if he needs surgery, the paper said.
"Even Marca gets it wrong," federation chief Gilberto Madail said, adding that he was hopeful Ronaldo would play against Bosnia in Lisbon on November 14 and in Zenica four days later.
"Ronaldo wants to play, he will join the squad and will be examined by the medical team.
"The situation is under control as there have been contacts between our coach, the Real Madrid coach, the player and the medical departments."
