Henri Behar, who moderates Cannes' news conferences, read a message from Pitt, who has been in Namibia with his "Mr. & Mrs. Smith" co-star, Angelina Jolie, awaiting the birth of the couple's first child.
"With the imminent arrival of the newest addition to our family, I am unable to join Alejandro, Cate, Gael and the rest of the cast and crew in introducing" his new film, "Babel," the 42-year-old actor said in the message.
"I am tremendously proud of `Babel' and want to congratulate everyone involved for this great achievement," Pitt said.
In "Babel," directed by Alejandro Gonzalez Inarritu, Pitt plays a husband and father trying to cope with a crisis on vacation in Morocco.
Cate Blanchett plays Pitt's wife, and the film also stars Gael Garcia Bernal.
Jolie's children, Maddox and Zahara, have legally had their surname changed to Jolie-Pitt.