(Cover) - EN Showbiz - Jennifer Lopez is reportedly on the verge of a custody battle with her estranged husband.

In July it was announced that the singer and Marc Anthony were divorcing after seven years of marriage. At the time it appeared the split was amicable and the pair vowed to remain on good terms for the sake of their two children.

However, Us Weekly are now reporting that Marc was furious after seeing a photograph of Jennifer's new boyfriend Casper Smart spending time with three-year-old twins Max and Emme.

Although Jennifer currently has primary custody of the kids, Marc has allegedly decided he wants to revise the arrangements.

"[He] hit the roof," as source told the publication. "It caused a huge blow up.

"He's going back on his word and saying his wants joint custody."

The photograph which is believed to have sparked Marc's rage was taken during a Thanksgiving vacation in Kauai, Hawaii. Jennifer and Casper decided to celebrate the holiday with the twins by taking a relaxing beach break.

It has been alleged that Marc is unhappy that Jennifer has moved on so quickly and is now dating the back-up dancer. He is also upset that Casper appears to be bonding with his kids.

"He wants to make Jennifer suffer because she's having fun with someone new, and he knows this will hurt her on the deepest level," the insider added.

However, sources close to Jennifer insist she would do anything to preserve her custody agreement if Marc does launch another legal battle.

"[Jennifer] is ready to smash him if he tries anything It's getting vicious," the insider revealed. (C) Cover Media