“Jackie,’’ Pablo Larraín’s new movie about Jacqueline Bouvier Kennedy, premiered at the Venice Film Festival Wednesday, and critics were nearly unanimous in their approval of the Chilean director’s first English-language film. Variety called the movie, which stars Natalie Portman as the former first lady, a “brilliantly constructed, diamond-hard character study,’’ while The Hollywood Reporter said the movie is “extraordinary in its piercing intimacy and lacerating in its sorrow.’’

Speaking to reporters in Venice, Larrain, whose 2012 film, “No,’’ was nominated for an Oscar, said “Jackie’’ is not intended to be a biopic. He said he was striving for something else. “I remember the first day of shooting, we had set up the camera and [Portman] just kept walking towards the camera — and that was the movie,’’ he said “I wanted to be very, very close and intimate. . . . I believe [Jackie Kennedy] was someone incredibly mysterious, one of the most unknown known people.’’ Larrain said he didn’t worry that Portman doesn’t particularly resemble Kennedy. “Sometimes I feel you can be at risk when you try to make the actor look just like the person and you work just on that and then the movie starts and it’s like a photo,’’ he said. “Natalie does a great imitation, but it could not sit there. With the tools of cinema, we tried to create an illusion.’’

Portman, who won the Oscar for her performance in “Black Swan,’’ said playing Kennedy was among the most challenging roles of her career. “It felt like the most dangerous,’’ she said. “Jackie’’ also stars Peter Sarsgaard, Billy Crudup, Greta Gerwig, and John Hurt.