The Ballon d'Or winner, who missed today's training session with a left thigh problem, has not been given a deadline for his return.
"He will be with us, but he will not compete," Bento told reporters in a press conference. "We don't have deadlines [on his return].
"The physical well-being and health of the player is our main concern and we will not set a time limit for the return to competition. We must leave Ronaldo and other players to recover in the best possible way and without risks."
Portugal will face Germany, Ghana and the United States in Group C in Brazil next month.