BOSTON (AP) – Ernest Hemingway wrote letters so filled with longing and devotion to actress Marlene Dietrich – sometimes signing off “I kiss you hard” – that it’s difficult to believe the pair never became lovers.

The correspondence between the icons, who met aboard an ocean liner in 1934, reveals a complex, flirtatious relationship in which they propped each other up and spoke unvarnished truth about each other’s romantic relationships, work and friends.

Thirty letters, cards and a telegram Hemingway wrote to the German-born actress and singer – whom he called “my little Kraut” and “daughter” – between 1949 and 1959 were made publicly available for the first time Thursday at the Ernest Hemingway Collection at the John F. Kennedy Presidential Library and Museum in Boston.

Hemingway, the self-appointed “Papa” of the literary world, defended his friendship with actress Ingrid Bergman in a letter to Dietrich dated May 23, 1950.

“In the meantime, if you are angry at me stay angry as long as you want. But stop it sometime daughter because there is only one of you in the world, nor will there ever be another, and I get very lonely in this world with you angry at me,” he wrote.

The letters were donated to the library in 2003 by Dietrich’s daughter, Maria Riva, on the condition that they be kept private until now. The library already held 31 letters and telegrams Dietrich sent to Hemingway during the correspondence.

Hemingway was 50 and Dietrich was 47 when their letter writing began in 1949.

Hemingway described the relationship to his friend, writer A.E. Hotchner, by saying he and Dietrich fell in love when they met aboard the Ile de France but “we’ve never been to bed. Amazing but true. Victims of un-synchronized passion. Those times when I was out of love, the Kraut was deep in some romantic tribulation, and on those occasions when Dietrich was on the surface and swimming about with those marvelously seeking eyes, I was submerged.”

Hemingway typed his letters to Dietrich on a manual typewriter. In a letter dated June 19, 1950 – at 4 a.m. – the Nobel Prize-winning author wrote: “You are getting so beautiful they will have to make passport pictures of you 9 feet tall. What do you really want to do for a life work? Break everybody’s heart for a dime? You could always break mine for a nickel and I’d bring the nickel.”

In a 1951 letter to Hemingway, Dietrich began, “Beloved Papa, I think it is high time to tell you that I think of you constantly. I read your letters over and over and speak of you with a few chosen men. I have moved your photograph to my bedroom and mostly look at it rather helplessly.”

On Nov. 21, 1951, Hemingway sent a letter to Dietrich’s apartment on New York City’s Park Avenue from his villa in Cuba and described his work on his novel, “The Old Man and the Sea,” amid the stifling tropical heat.

“I’d get up at five or six o’clock for the cool of the morning and knock off when you couldn’t write anymore because you would sweat the paper through.I never worked better and tried to keep cool with the pool and sent Mary away for vacation where it was cool,” he wrote. “It was too hot to make love if you can imagine that except under water and I was never very good at that.”

Hemingway’s fourth wife, Mary, chose the library as the repository for the bulk of his papers after becoming a close friend of Jacqueline Kennedy Onassis. Members of the general public can view the collection by appointment.

Peter Riva, Dietrich’s grandson, said the correspondence between his grandmother and Hemingway should be considered in its entirety to best understand the pair.

“What Hemingway and Dietrich had was a relationship that allowed them to be at times the succor of the other, at times the analyst of the other, but always to be the mirror, the truth-sayer to the other,” Riva said.