Kevin Mazur / WireImage 1 / 8
Kevin Mazur / WireImage 1 / 8

By Kat Giantis

Things may be about to turn ugly for once-friendly exes Halle Berry and Gabriel Aubry. Two weeks after the Canadian model filed legal papers to be formally recognized as the father of 2-year-old daughter Nahla and to confirm that he shares custody with the Oscar winner, she's preparing to duke it out in court.

"Halle has serious concerns for her daughter's well-being while in the care of her father for any extended period of time," her rep informs People, Us and TMZ, "and is prepared to take all necessary steps to protect her."

According to the spokesman, "She has attempted to resolve these custody issues amicably" with Aubry, "but given his lack of cooperation, Halle has no choice but to seek swift judicial intervention."

In order to prepare for the legal battle, the A-lister has dropped out of "New Year's Eve," the follow-up to the critically eviscerated "Valentine's Day," which was due to start filming this week in New York. Katherine Heigl has stepped into Halle's vacated role.

VIDEO: Halle Berry Fights for Custody

The custody move comes amid talk that relations between the duo have grown decidedly frosty in recent weeks.

"Basically whenever Gabriel doesn't do exactly what Halle tells him to do, or if he does something she doesn't approve of or like, she goes crazy on him, screaming and shouting," a source recently alleged to RadarOnline.

Declares her rep, "Halle has always made the needs and safety of her daughter her first priority and, both while Halle and Gabriel were a couple and since their break-up, Halle has only acted in her daughter's best interest."

Berry has said her four-year-plus relationship with Aubry was her longest to date, and after their breakup last spring, she publicly praised his parenting skills.

"We're still friends, we love each other very much, and we both share the love of our lives," she told the September 2010 issue of Vogue. "And while it was not a love connection for us, he was absolutely the right person to have this child with because she is going to have an amazing father."

RELATED: More of Halle in Vogue

The exes spent time together after their split for Nahla's sake, with Gabriel tagging along on Halle's film shoots in order to stay close to his ridiculously cute daughter.

Last summer, he jetted to South Africa while she filmed "Dark Tide," where she met current squeeze Olivier Martinez.

Over the weekend, Halle and Olivier ventured out for a photo-op on a Malibu beach, with the actress seemingly making a point of putting her bauble-covered ring finger on prominent display.

She denied engagement rumors last week.

Talk of a custody battle has been percolating since shortly after their breakup last spring, when Aubry was supposedly so upset over the resulting publicity that he was rumored to be considering fighting for the right to return to Canada with Nahla.

Of course, back in November, Aubry brought the spotlight on himself when he kicked off a short-lived romance with Kim Kardashian, a move that reportedly didn't sit well with his ex.

"We were meant to bring this amazing little person into the world," Halle told Vogue of Gabriel. "And I think that's why we came together. And because of that, we are going to be together forever, all three of us."

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