John F Kennedy was portrayed as happily married but had many affairs
Secret love letters written by former US President John F Kennedy to a Swedish woman are being put up for auction.
The letters were written to Gunilla von Post when Mr Kennedy was an ambitious US senator in the 1950s.
Their love affair began before Mr Kennedy married Jacqueline Bouvier - but continued afterwards.
Bidding for the letters starts at $25,000 (£16,000), but they are expected to fetch much more.
Ms Von Post, now 78 years old, revealed her affair with the former US leader in a 1997 book, but the 11 handwritten letters and three telegrams have remained private until now.
In an interview with US broadcaster ABC News in 1997, she said her heart went "boom boom boom boom" when she was with Mr Kennedy.
"I was very happy to hear from him, but I said 'He's a married man'," she said.
The two first met on the French Riviera in the summer of 1953 when Mr Kennedy was 36 and Ms Von Post was 21, ABC reported.
Despite being only a month before Mr Kennedy's marriage, they danced all night and parted with a romantic kiss.
Mr Kennedy wrote his first letter to the Swedish beauty in June 1954.
Letters were often written on senate stationery Pic: legendaryauctions.com
In it he wrote: "I might get a boat and sail around the Mediterranean for two weeks - with you as crew."
But in November 1954 Mr Kennedy underwent major surgery on his back and wrote to Ms Von Post from a New York hospital asking: "Is there any chance you will be coming to the US?"
The following year the two secretly met at an old castle in Sweden.
"I borrowed him for a week, a beautiful week that no-one can take away from me, from that," Ms Von Post told ABC.
In the last letter - dated August 1955 - Mr Kennedy wrote: "I just got word today - that my wife and sister are coming here. It will all be complicated the way I feel now - my Swedish flicka [Swedish for little girl]. All I have done is sit in the sun and look at the ocean and think of Gunilla. All Love, Jack."
Mr Kennedy had numerous affairs which only came to light after his assassination in 1963.
Chicago-based Legendaryauctions.com is taking online bids for the letters.
Auction house president Doug Allen told ABC he believes the letters should fetch up to $100,000.