'Star Wars': Carrie Fisher Reveals 'Intense' Harrison Ford Relationship

— -- The Force is strong with them.

It's been 40 years since "Star Wars" hit theaters in 1977, and more importantly, since Han Solo first met Princess Leia while trying to save the galaxy from the Death Star and the Empire.

But for the first time since Carrie Fisher played the plucky, passionate Leia and Harrison Ford played the wise-cracking, yet reluctant hero Solo, the 60-year-old actress is opening up about an "intense" off-screen affair she says took place when the cameras weren't rolling.

Fisher, who writes about the affair in her new memoir "The Princess Diarist," says it took place over three months while filming "A New Hope" in 1976.

“It was so intense,” she tells People magazine. "It was Han and Leia during the week, and Carrie and Harrison during the weekend."

Fisher was 19 at the time, while Ford was 33.

A rep for Harrison Ford did not immediately return ABC News' request for comment about Fisher's claims. She tells People he knew about the upcoming book.

The two recently reunited on-screen again as Leia and Han in last year's "The Force Awakens," which also had an appearance from Mark Hamill's Luke Skywalker. In the film series, Han and Leia fall in love and eventually have a son.

About their romance four decades ago, Fisher adds, "I was so inexperienced, but I trusted something about him. He was kind.”