NEW YORK (AFP) ― John F. Kennedy carried on an 18-month-long affair with a teenaged White House intern, according to a new book by the woman who claims to have been the late U.S. president’s lover.

Excerpts of the shocking memoir, “Once Upon a Secret: My Affair with President John F. Kennedy and Its Aftermath,” were released Monday by the New York Post, which said it purchased a copy of the book at a local bookstore, although it is not scheduled for publication until Wednesday.

In her tell-all memoir, author Mimi Alford, now a 69-year-old grandmother, recounts the president’s tears after the death of his newborn son, and recalls that he confided to her, while embroiled in the drama of the Cuban missile crisis that “I’d rather my children red, than dead.”

Alford provides intimate details of their relationship, which started in the summer of 1962, when she was just 19, less than half the age of the dashing president, who was killed the following year by an assassin’s bullet at the age of 46.

In an excerpt published by The Post, Alford wrote that she met Kennedy just four days into her internship, and that he invited her the following day on a personal tour of the White House residence that included first lady Jackie Kennedy’s bedroom.

Now 50 years later, Alford, a retired New York City church administrator, writes that it was there that she lost her virginity to Kennedy that day.

“Slowly, he unbuttoned the top of my shirtdress and touched my breasts,” Alford ― at the time Mimi Beardsley ― wrote in the excerpt.

“Then he reached up between my legs and started to pull off my underwear. I finished unbuttoning my shirtdress and let it fall off my shoulders.”

“After he finished, he hitched up his pants and smiled at me” before pointing her in the direction of the bathroom, the Post reported.

“I was in shock,” Alford wrote.

“He, on the other hand, was matter-of-fact, and acted as if what had just occurred was the most natural thing in the world.”

The young debutante, described by one Kennedy biographer as a “tall, slender, beautiful” college sophomore, continued the relationship for a year and a half ― even traveling with the president on occasion ― until their affair ended with Kennedy’s assassination.

Although they never kissed, and there was always a layer of reserve between us, the sex was “varied and fun” she said, although Kennedy sometimes “acted like he had all the time in the world. Other times, he was in no mood to linger.”

During their affair Kennedy reportedly taught Alford to make scrambled eggs and to appreciate the music of Frank Sinatra and Tony Bennett. Despite their intimate liaison, she continued to call him Mr. President.

And she explains in her book that it never occurred to her to resist the advances of the leader of the free world.