Sporting right-back Pereira has been called up for the first time and may fill the vacancy left by the international retirements of Miguel and Paulo Ferreira.
Midfielder Machado also earned a squad place after impressing at French club Toulouse.
Bento recalled midfielders Joao Moutinho and Carlos Martins, and striker Helder Postiga, all of whom had been left out of recent Portugal squads and missed the World Cup.
Bento last month replaced Carlos Queiroz, who was sacked in the wake of a suspension for insulting anti-doping agents, and the new coach has the task of rescuing qualification after a dismal start to the campaign.
Portugal are second from bottom of Group H with one point from their first two qualifiers having lost 1-0 in Norway following a 4-4 draw at home to Cyprus.
Bento said forward Cristiano Ronaldo would remain team captain.
"I think he has every condition to play that role," Bento told reporters.
Squad:
Goalkeepers: Beto (Porto), Eduardo (Genoa), Rui Patricio (Sporting).
Defenders: Bruno Alves (Zenit St Petersburg), Fabio Coentrao (Benfica), Joao Pereira (Sporting), Ricardo Carvalho (Real Madrid), Rolando (Porto), Silvio (Braga).
Midfielders: Carlos Martins (Benfica), Joao Moutinho (Porto), Pepe (Real Madrid), Miguel Veloso (Genoa), Paulo Machado (Toulouse), Raul Meireles (Liverpool), Tiago (Atletico Madrid).
Forwards: Cristiano Ronaldo (Real Madrid), Danny (Zenit St Petersburg), Helder Postiga (Sporting), Hugo Almeida (Werder Bremen), Liedson (Sporting), Nani (Manchester United), Varela (Porto).
