SHOCKING never-before-seen photos of Julia Roberts in a steamy love tryst with another man are forcing beau Benjamin Bratt to rush down the aisle.

America’s top movie star has kept a close relationship with former boyfriend Ross Partridge – – and exclusive ENQUIRER photos show how the hunky bartender-turned-actor unleashed Julia’s wild side.

Even as she romanced Bratt, the 33-year-old beauty has stayed in close contact with Ross, cozied up with ex-beau Jason Patric and even hung out on her new movie set with skirt-chaser Bruce Willis.

“Julia can be a real wild child,” author Frank Sanello, who wrote the unauthorized bio “Julia Roberts: Pretty Superstar,” told The ENQUIRER.

“One of her favorite places is Hogs & Heifers in New York, where she’s been known to jump up on the bar, dancing and slipping off her bra!”

It all adds up to a clear message for Bratt: make a commitment or say goodbye!

“Simply put, Julia is using jealousy to become Mrs. Benjamin Bratt,” an insider believes.

“She’s pulling out all the stops to get Ben to commit by the end of the year.

“Although Julia and Ben have been posing as the happiest couple in Hollywood while she enjoys the hoopla around her Academy Award nomination, there’s been trouble in paradise.

“Rumors swirled last year that Ben was cheating on Julia while filming ‘After the Storm’ in Central America. Julia bristled when she heard that Ben was extra close with co-star Mili Avital as well as partying with two of the local lovelies.

“A jealous Julia flew down to the jungles of Belize to put out any possible fires in the relationship — and now she is determined to avoid any more flare-ups.”

Although Julia loves Ben, he gets cold feet when she broaches the idea of marriage.

So she’s unleashed a “secret weapon” in her campaign to get him to commit — and that weapon’s name is Ross, says the insider.

“She has gone to great lengths to let Ben know that her relationship with Ross was passionate. Julia and Ross had many a wild night painting the town red when he was a bartender at the swinging Le Colonial restaurant in Hollywood.”

The sizzling exclusive ENQUIRER photos capture the passion and intensity of their love affair, a stark counterpoint to the reserved public outings of Julia and Bratt.

“Julia and Ross were introduced to each other by actor-friend Kevin Spacey, and for several months they were crazy for each other.

“They hit late-night Hollywood spots and were all over each other like white on rice. They didn’t care who was watching — and the newly discovered photos will certainly help Ben realize just how passionate the two really were.

“Julia and Ross are kindred souls. They talk and exchange e-mails all the time — and Julia dragged Ben along to a gathering she knew Ross would attend about six months ago. They caught up on old times with warm hugs and kisses under Ben’s watchful eye.

“Afterward, Ben let Julia know how little he cared for the ‘old home week’ get-together.

“But Julia has not stopped there.

“She’s recently been spotted hanging out with Bruce Willis as well as with old beau Jason Patric. She was even photographed embracing Patric.”

It appears that Julia’s tactics are succeeding — and Ben, 37, is clearly turning green, divulged a close source.

“Julia made Ben boiling mad with jealousy when she was spotted in a clinch with her old flame, handsome Jason Patric.”

Stirring the pot even more, notorious womanizer Bruce Willis jetted to the Vegas set of Julia’s new movie “America’s Sweethearts.” He said he flew in from Idaho with one of his daughters to visit the movie’s director, Joe Roth.

“Still, having Bruce there couldn’t have made Ben feel any better since it was rumored in Hollywood that Julia and Bruce once enjoyed a torrid tryst,” said an inside source.

On February 10, the fun-loving actress showed she still knows how to kick up her heels and have a good time — with or without Ben. The evening started nicely enough with Julia and cast mate Catherine Zeta-Jones — along with a group of crew members — singing Beatles songs around the piano in the lobby of the Hyatt Regency Lake Las Vegas hotel.

“Then about 5 a.m., the giggling gals were spotted at the hotel Jacuzzi, where they doffed their bras and bikini bottoms and skinny-dipped with their body doubles!” said the inside source.

Security guards had to break up the frolicking foursome at 6 a.m. for fear the popular actresses would be spotted by attendees of an early morning breakfast event.

Concluded the inside source:

“Julia is using every trick in the book — plus Bruce Willis, Jason Patric and Ross Partridge — to get Ben to say, ‘Will you marry me?’ “

And author Sanello added: “The bottom line is, despite some bumps in their relationship, Julia and Ben have a very strong emotional bond. I’m certain they’ll get hitched because Julia wants to be married to Ben.”