NICOLE KIDMAN is reeling from a perfect storm of setbacks that have turned her world upside-down – and friends fear the fragile actress is headed for a major breakdown.

“Those closest to Nicole are deeply concerned about her fragile emotional and physical state,” divulged an insider. “She’s been withdrawn and canceling plans with friends. She also looks glum and worn-out lately.”

Sources say the Australian beauty has been strug­gling to cope with long sepa­rations from her husband Keith Urban. She’s also immersed in a firestorm of controversy surrounding her biopic about Princess Grace and said to have been shattered by the suicide of her close friend L’Wren Scott.

“Nicole has admitted that sometimes she feels like the world is caving in on her,” the source confided. “She struggles to keep up the facade of a work­ing mom who’s able to juggle crazy work demands with family life while keeping her husband happy and satisfied.

“Even when she’s smiling in public, she’s just hiding the pain. At home, Nicole sometimes just lies in bed and cries. It’s tragic.”

Nicole has apparently reached the breaking point in her nearly eight-year marriage to country singer and “American Idol” judge Urban. Sources say she’s no longer able to handle the extended periods of time apart as they each juggle their hectic careers while raising their two young daughters, Sunday, 5, and Faith, 3.

Reports have sur­faced that Nicole is facing a $175 million divorce showdown with Keith – a recov­ering cocaine and alcohol addict – over fears that he’ll stray while they are work­ing on opposite sides of the globe.

“She has serious trust issues,” said the source, “and no mat­ter how much Keith tries to reassure Ni­cole, she fears the worst.”

In the past six months, Nicole, 46 – who was married to Tom Cruise for 11 years – has shot movies in London, Morocco and, most recently, a drama called “Strangerland” in Australia.

“Nicole has been ping-ponging around the globe with barely a chance to catch her breath,” said the source.

Meanwhile, Keith – who at­tended the Academy of Country Music Awards solo on April 6 – has been taping “American Idol” in Los Angeles. But he’s also been touring North Amer­ica during breaks from the FOX singing competition and plans to continue touring through the summer.

It’s been reported that Nicole and Keith have been doing a lot of long-distance arguing over the past few months – and that they had a huge blowout over Keith’s onscreen flirting with fel­low “Idol” judge Jennifer Lopez.

Adding to her marital stress, Kidman was shattered by the death of her best friend, design­er L’Wren Scott. The girlfriend of Rolling Stones rocker Mick Jagger, Scott tragically hanged herself in her New York City apartment on March 17.

Nicole, who fre­quently wore Scott’s designs on the red carpet, “was devastat­ed beyond words,” her rep said, adding: “Ni­cole and L’Wren were close friends for 25 years. Nicole is heart­broken and in shock right now and unable to say anything.”

Topping off Ni­cole’s grief is the furor over her new movie “Grace of Monaco.” As The ENQUIRER reported recently, Grace Kelly’s kids – Prince Albert and Prin­cesses Caroline and Stephanie – slammed the biopic and were planning to boycott the May 14 premiere at the Cannes Film Festival.

And in a highly unusual move, Monaco’s royal family formally denounced the film for a SECOND time, releasing a scathing statement in which they call the movie’s trailer “a farce” and “fictional.”

The statement says: “The Princely family does not in any way wish to be associated with this film which reflects no reality and regrets that its history has been misappropriated for purely commercial purposes.”

Then, to add insult to injury, Prince Albert singled out Nicole as being too old and completely wrong to play the role of his late mother, the Hollywood-actress-turned-princess who died in a car crash in 1982 at the age of 52.

All eyes will be on Nicole to see how she handles the pressure when she hits the red carpet in Cannes. Not only has the royal family blasted the film, now there are reports that producer Harvey Weinstein wants the French directors to re-edit the movie for U.S. release – and they’re refusing to do it. That means “Grace of Monaco” may NEVER reach American au­diences, thus ruining Nicole’s dream of winning another Oscar for the role.

“Keith is begging Nicole to dial back her work commitments and chill out,” said the source. “But she’s ignoring his pleas and plow­ing forward in promoting ‘Grace of Monaco’ because she wants to save face and is desperate to maintain her A-list actress status.

“Nicole is feeling her age right now and she’s worried that young up-and-comers like Jenni­fer Lawrence and Kristen Stewart are nipping at her heels.

“During low times, Nicole al­ways buries herself in work. So for Nicole’s personal and profes­sional lives to both be faltering at the same time is almost too much to bear.”

For now, Nicole’s friends are keeping their fingers crossed that she will be able to pull through the dark days and get her marriage back on track.

“Otherwise,” the source warned, “Nicole could be headed for a catastrophic breakdown.”