In A desperate effort to revive their romance, O.J. SIMPSON is bombarding Kris Jenner with love letters from his jail cell, The ENQUIRER has learned.

Kris, 58, has always denied shocking reports that she cheated on her first husband with The Juice, who’s been rotting behind bars in Nevada ever since his 2008 robbery conviction.

But sources insist the duo had an illicit affair in the mid-’80s while Kris was married to Simpson’s best buddy, Robert Kardashian. Now, with all the time in the world on his hands, Simpson has developed a fixation on his former flame!

“O.J.’s desperate for face time with Kris and has been laying it on thick in his letters, telling her how beautiful he thinks she is and what wonderful memories he has of their time together,” revealed an insider.

“He’s told her she’s one of the sexiest, most intelligent women he’s ever met – and he wishes things had turned out differently between them. “Obviously her power and money is a huge attraction to him, as well as her looks – and he’s clearly got it in his head that her cash could get him an early release.”

Disclosed a close source: “It’s Kris’ worst nightmare! She wants no part of O.J., but he’s pleading with her to visit him in jail and go over some very important issues that he wants to discuss with her in person.

“He has a lot of dirt on Kris from the old days, so it will be in her best interest to visit him, whether she wants to or not.”

As The ENQUIRER disclosed, Simpson and Kris were party buddies back when she was best pals with Simpson’s wife, Nicole Brown. The relationship soured following Nicole’s brutal murder in 1994, and Kris later wrote in her autobiography that she suspected Simpson had a part in the heinous crime.

Besides romance, Simpson has another startling motive for his jailhouse pleas to Kris. He wants answers about longstanding rumors that he is the birth father of her daughter, Khloé Kardashian!

“He wants to hear it from her – and if there’s a trace of doubt when she answers, he’ll fight tooth and nail for a DNA test.”