The Real Madrid forward has been blighted by injuries in recent weeks and has not featured for the Spanish capital club since sustaining a muscle problem in a 1-1 draw at Real Valladolid earlier this month.
Ronaldo is still expected to feature in the Champions League showpiece with city rivals Atletico Madrid in Lisbon.
Portugal coach Paulo Bento confirmed his staff are in contact with Real's medical department and are set to evaluate the national team captain following the all-important clash with Atletico.
"We have some information about Cristiano Ronaldo, due to the contact between the medical department of the Portuguese national team with Real Madrid," Bento said.
"Now, after Saturday's Champions League final, we can see how he will end the season and evaluate his full fitness when he is with us.
"Once he arrives, we will try to make a plan for everything so that we can start the World Cup in the best possible shape.
"It is very difficult to compare Cristiano Ronaldo with anyone. What I can guarantee is that any team, and our selection is no exception to the rule, will always be stronger counting on a player like him, for the reasons that everyone knows.
"What we expect is, when he is under our care, we will work with him as best we can and of course, talk to him, talk to the medical department and then we can get the best decision of how much he can play, both for him and the Portugal team."
Portugal, whose provisional squad was cut to 23 men on Monday, face friendlies with Greece, Mexico and the Republic of Ireland before starting their World Cup campaign against Germany in Salvador on June 16.
Bento's men, who have been drawn in in Group G, will then face United States and Ghana as they bid to reach the knockout stages.
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