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Intimate love letters penned by President John F. Kennedy to his Swedish mistress are up for sale. 

The handwritten letters Kennedy wrote to Swedish aristocrat Gunilla von Post are a part of RR Auction's Fine Autographs and Artifacts sale. 

The letters are estimated to sell for upwards of $30,000.  

'If you don't marry come over as I should like to see you,' one letter postmarked February 1956 reads. 

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'I had a wonderful time last summer with you. It is a bright memory of my life-you are wonderful and I miss you.' 

Von Post met Kennedy by chance in the summer of 1953 in the French Riviera. 

He was then a Massachusetts U.S. Senator and just weeks away from marrying Jacqueline Bouvier, later known as Jackie Kennedy.

For the next three years, the two exchanged letters back and forth across the Atlantic, with Kennedy even planning to leave his wife for the von Post, according to her 1997 memoir 'Love, Jack'.

The two reportedly spent a week together in Sweden in August 1955, according to von Post's memoir. 

They saw each other again only one time, by chance at a gala at the Waldorf Astoria in 1958 while von Post was pregnant with her first child. 

The auction includes the original hand-addressed United States Senate envelope. 

'This is the only Kennedy letter that we have offered that displays open affection to another woman while he was married,' RR Auction's Fine Autographs and Artifacts notes. 

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The first partial letter from circa 1955 reads: 'Dear Gunilla, I must say you looked well and happy in the photograph you sent me at the Regatta. 

'What does "Lagsamling Pa Dack Fore Regattan" mean? Something awful I'm sure. 

'It now appears that Congress will not finish until the 5th of August-so I sail on the 'United States' which arrives the 10th of August at Le Havre-and I shall be in Sweden on the 12th. Where do I go. Send me your address at Bastaad where you shall be.' 

The second partial letter, signed 'Jack', reads: '.coming and perhaps you could make me a reservation. I am anxious to see you. 

'Is it not strange after all these months? Perhaps at first it shall be a little difficult as we shall be strangers-but not strangers-and I am sure it will all work and I shall think that though it is a long way to Gunilla-it is worth it.' 

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