“What are you talking about,” shouted Meryl Streep over the phone, “I`m not 48 years old.” She had been talking about the comment, made to her by a famous director, that he couldn`t find any traditional leading men in their 30s. “I guess it`s true,” she said, to which her caller replied, “Yes, I guess they haven`t been able to replace your generation-Hoffman and De Niro.” Dustin Hoffman, who costarred with Streep in “Kramer vs. Kramer” is 48 years old. De Niro is 41. Jack Nicholson, her latest romantic costar, is 49.

Streep has convincingly played their wives and lovers as well as other mature characters, such as Karen Blixen in “Out of Africa.” But she is nowhere near Hoffman`s 48. “I just turned 36,” she said to a shocked listener. Shocked because Meryl Streep, two-time Oscar winner and six-time nominee, has achieved a stature in the film industry that is best described as a young grand dame. Colleagues and moviegoers agree that when it comes to technical excellence Streep has no equal. Indeed, so often has the New Jersey native used a foreign accent flawlessly (as in “The French Lieutentant`s Woman,” “Sophie`s Choice,” “Plenty” or “Out of Africa”), that some people joke an American dialect has become her second language. “I like acting as a process of experimentation,” she said, explaining her strong interest in playing foreign characters. “I think acting is the ultimate in voyeurism. We get to go beyond looking; actors actually get to act out other people`s lives. So I have a strong desire to try to stretch myself as much as possible.” That stretching has been both a major blessing and a minor curse to Streep, at least in terms of the way some of us view her. “Too perfect,” “too brittle,” “too remote,” are comments one hears. “You`re often aware she`s acting,” is another. Streep knows the complaints well. “Pauline Kael (film critic of the New Yorker) can`t stand anything I do. So I`ve stopped reading her. She says my work has no heart, that it won`t last the centuries.

“But I can`t live my professional life worrying about the impact I might have in the future or the impact I`m having right now on a man in Arizona or a woman (Kael) who lives in Stockbridge, Conn. “I think if you start reacting to what part of the audience or media thinks of you, it can tie your legs. One thing is for sure. With most of the characters I`ve played I haven`t tried to keep the audience at a distance. I certainly didn`t want that for Sophie or for (Karen) Silkwood. “But I did want that distance for the woman in `Plenty.` The warmth that the audience should feel toward the character should vary with the character. So the varying reactions are not a problem. “Right now the biggest burden in my life,” Streep said with a laugh, “is that I`m carrying 155 pounds.” That`s her weight after the birth nine weeks ago of her third child, Grace Jane. She also has a son, Henry, 6, and a daughter Mary Willa (nicknamed “Mamie”), 2. “Honestly I don`t really understand the criticism of doing one`s job well,” she said. “Obviously when one does a film like `Plenty` or `Out of Africa,` you do it for reasons that have to do with the work and not with what the audience is going to think of you, if any audience shows up. “Frankly, I was surprised by how many regular people seemed to care about that woman in `Out of Africa` as well as that film.” But isn`t there a part of her that clamors to be loved in an old-fashioned movie-star way, rather than being admired as “only” a superior actress. “Not a bit,” Streep said. “First of all, I don`t think I have the kind of face that makes an audience love you. And in the movies with all of their close-ups, that`s very important. “I think I look like Dame Edith Sitwell (who looked more like E.T. than Streep). I think the actors and actresses who are loved generally have more cuddly features. “Beyond that, I have no interest in being adored as some kind of populist movie icon like Marilyn Monroe, if that`s what you`re getting at. That kind of stardom is a terrible burden. “For example,” she continued, “I had a fabulous time in Nairobi, but Redford didn`t. He couldn`t go out-even there. He was self-conscious all the time. I went everywhere, saw whatever I wanted to see. I felt sorry for him.” There is little reason to feel sorry for Streep. Performing live on stage is her only professional fear.

“It`s been seven years, and I guess I`ve grown comfortable being in front of a movie crew where everyone is rooting for you except the camera, which doesn`t want to hurt you. “Appearing live has become a problem. Last year, I had to present the best-actor award to Jack (Nicholson) at the New York Film Critics` dinner, and I was a basket case, speaking in front of them. It`s hard to live up to people who have such extreme opinions of you.” That aside, Streep is in complete control of her career. She commands her pick of the choicest roles. What actress didn`t want to play Sophie or Karen Silkwood? Streep was the first choice for both. She also led the list for her latest role, New York magazine food writer Rachel Samstat in “Heartburn,” a character based on the semi- autobiographical novel by Nora Ephron. In between comically delivering dozens of recipies, the book tells how Rachel`s Washington newspaper-columnist husband, Mark, carried on an affair during her two pregnancies. In real life, Ephron was married to and was divorced from Watergate journalist Carl Bernstein, who cried “foul” when he read the book and then learned that their broken marriage was going to be made into a major motion picture, opening Friday. At first, Mandy Patinkin (“Yentl”) was cast as Rachel`s husband; later, Jack Nicholson took the part, which seems surprisingly small, especially with Nicholson in it. “The script wasn`t changed to accommodate Jack,” Streep said. “It was always the same story.” Some viewers may find that story wanting in detail about Mark`s life away from his wife; others may want more scenes of pain and pleasure between them. “But it`s really the woman`s story,” Streep replied. “It`s not that much different, if you think about it, from `Kramer vs. Kramer,` where my character went away for a long time while the film focused on Dustin`s character. “Maybe (critics of `Heartburn`) find it difficult to get behind a female protagonist center stage,” she said. That may be true, particularly when it is Jack Nicholson who is offstage. “But there`s a great scene for Jack`s fans in the film,” Streep protested. “It`s the scene where I`m having the second baby, and he knows he`s been continuing the affair, and there`s a wash of regret across his face in what should be the happiest moment of our lives. “Jack played that scene so open, emotionally. That was special. I`ve worked with a lot of guys, and most of them are afraid of playing an a —. They`d rather cut up in front of the crew for approval. But Jack opened himself up completely and he did that scene five times.

“I mean `Kramer vs. Kramer` is a much more conventionally satisfying movie,” she continued, warming to her defense of “Heartburn.” “There`s a good guy in `Kramer` and a bad guy, and there`s a dramatic reversal at the end in which the good guy wins. I don`t know how that bears a resemblance to reality.” Oddly enough, the years between the making of “Kramer” (1979) and “Heartburn”-both stories of broken marriage-correspond almost precisely to the length of the successful marriage between Streep and sculptor Don Gummer, 39. They recently purchased a home in Connecticut, leaving her Greenwich Village apartment behind as their primary residence. Given her apparent success in marriage, Streep was asked if she thought she knew anything for sure about the institution, especially having voyeuristically played with its failure so often on film. (Characters she played had extramarital affairs with Alan Alda in “The Seduction of Joe Tynan” and Robert De Niro in “Falling in Love.”) “Well, I know I love mine,” she said immediately. “Yes, I saw `Heartburn` with Don. No, I didn`t once think to myself, `I wonder if he`s had an affair?` “I guess all I can say about marriage is that I think you have to look at it as sort of a muscular organism that you have to keep working out. To continue the workout analogy, you have to, as they say, `go for the burn.` You have to work hard at it, exercising every part of it. “A friend of ours who is a lawyer saw `Heartburn` and knows the statistic that half of today`s marriages will end in divorce. He said, `The problem is they`ve made the divorce laws easier.` “But I think that`s only part of it, that he`s looking at it only from his professional, legal point of view. “I do know this is true: It is much easier in our minds to get a divorce. That`s probably true. I wonder why.” It was suggested that Streep`s generation-now that she had identified herself as a 36-year-old-was quick on the trigger to avoid pain and seek pleasure. “I think that`s true,” she said. “That must be part of it. But I don`t know if either `Kramer` or `Heartburn` should be viewed as offering answers. I don`t think they`re emblematic of all marriages.

“They`re simply two stories. `Kramer` was written by Avery Corman (as a novel first), and I believe he made it all it up. `Heartburn` came directly from Nora Ephron`s own experiences. So I don`t think you can draw too many conclusions about marriage from them. I view them just as examples of two marriages, much as I would view the marriages of two couples I know.” As for her professional future, Streep volunteered that anyone who didn`t get enough of her and Nicholson in `Heartburn` would soon get a second chance: “We`re in (the film of novelist William Kennedy`s) `Ironweed` together, which is my next movie. It`s a Depression-era story. Jack plays a down-and-out, haunted baseball player; I`ve hit the skids, too. I get to play two things I`ve always wanted to play-a singer and a drunk.” A new sound was heard in the background of Streep`s house. It was baby Grace, who wanted some attention. Meryl Streep, actress and mother-but not icon-wanted to give her infant daughter all the care she wanted. There was nothing more to say.