Injury worries for Ronaldo
Ronaldo, 29, had several concerns late in the domestic season, but fought through and helped Real Madrid win the UEFA Champions League and Copa del Rey.
But he is yet to train with Portugal, who face Germany, Ghana and the United States in Group G, due to 'some problems'.
Bento said he would happily wait for Ronaldo until the superstar was ready, with Portugal's friendly against Greece on Saturday coming too soon.
"He was evaluated and presents some problems," Bento said.
"We know that he made the match for his team, with some limitations . And a game that went to extra-time.
"We will not stipulate any deadline for him to come back to training."
Bento said his team were entering the World Cup below their best, but hopes they are ready to adapt to different situations.
"Portugal will have to be a team with players who aren't at their optimum," he said.
"But we will also have to compete with different players and strategies that may not normally ones we would be used to."