Lisbon - Cristiano Ronaldo, who is still feeling the effects of a thigh injury, and Real Madrid teammate Pepe will both miss Portugal's World Cup warm-up match against Brazil-bound Greece on Saturday.
Ronaldo sustained the injury late in the season, but Bento said there was no specific timetable to get the Portugal captain back on the pitch.
"We're not going to set down a calendar for his return to competition," Bento said, adding that he wanted to take "no risk".
Central defender Pepe, making his comeback after a calf injury, trained on Thursday and Friday, having remained on the bench during Real's Champions League final victory over Atletico Madrid last Saturday, Ronaldo having played all 120 minutes in that match.
Portugal leave Monday for the United States where they will play Mexico and the Republic of Ireland in friendlies.
The Portuguese have been drawn in Group G at the World Cup and will face Germany on June 16 in Salvador, the United States a week later in Manaus and then Ghana on June 26 in Brasilia.