The Sunderland striker, who is currently on loan at Crystal Palace, replaces Damien Duff who has been sent home with a hamstring injury.
Celtic winger Aiden McGeady is also struggling with a foot injury, in a situation that has led to manager Giovanni Trapattoni's decision to strengthen his options.
The Irish camp are hopeful that McGeady, who has a badly-bruised right foot, will be available, although that will depend on whether he is able to join in training with his team-mates on Friday.
If he does not make it, the Italian will have to assess his options, and Stokes' arrival will give him more cover.
Ireland assistant boss Liam Brady said of McGeady: "I think it's more likely that he will play but we won't know until he comes through the training session today.
"We have kept him out of contact, his foot is still badly bruised. But with bruising, the longer it goes on, the better it gets.
"The manager will want to see some kind of contact today and comfort when he is kicking the ball.
"We have got to have fit players out there. We believe he will make Saturday but it's the type of injury that if he doesn't make Saturday, he will make Wednesday."