Image caption The book gives Ms Alford's impressions of key moments in Mr Kennedy's presidency

A book by a former mistress of President John F Kennedy has revealed new details of their relationship.

Extracts in the US media of Once Upon A Secret by Mimi Alford recount the affair she had with the president whilst an intern at the White House.

She also relates Mr Kennedy's thoughts on the Cuban missile crisis and the death of his baby son.

The previewed parts of the book contain graphic details of the president's milieu, including tales of drug use.

Excerpts published in the New York Post also describe how Ms Alford - then 19-year-old Mimi Beardsley - lost her virginity to the president in 1962, after she had been invited to swim at the White House pool.

The affair went on to last 18 months.

The relationship apparently continued even after Ms Alford left Washington, and she claims to have slept with Mr Kennedy just days before he was assassinated.

Ms Alford, now 69, also recalls consoling Mr Kennedy after the death of his baby son Patrick.

Image caption Ms Alford's decision to write the memoir came after being exposed in "a tabloid frenzy"

"There was a stack of condolence letters on the floor next to his chair, and he picked each one up and read it aloud to me... Occasionally, tears rolling down his cheeks, he would write something on one of the letters, probably notes for a reply.

"But mostly he just read them and cried. I did, too," Ms Alford writes, according to the New York Post.

Alford also claims that at the height of the Cuban missile crisis, Mr Kennedy may have been willing to give ground.

She claims he confided that "I'd rather my children were red than dead".

Ms Alford's decision to write the memoir came after being exposed in "a tabloid frenzy" in 2003 when a Kennedy biographer had referred to "a 19-year-old... White House intern" as one his affairs, according to her publisher, Random House.