Looks like Britney Spears and ex-husband Kevin Federline are gearing up for a contentious child support battle in court.

On Monday, a source close to Federline told ET that the former dancer – who’s had full custody of his and Spears’ two sons together, Sean Preston and Jayden James, since 2008 – wants an increase in child support given Spears’ huge success with her Las Vegas residency and worldwide tour, Britney: Piece of Me. On Tuesday, Federline’s powerhouse L.A. divorce attorney, Mark Vincent Kaplan, confirmed to ET that his client – who gets about $20,000 a month in child support – would like at least double what he’s currently getting, and is willing to take Spears to court to get it.

In response to Federline’s request for a significant increase in child support, a source close to the pop star claims to ET that Spears already covers most of their sons’ expenses, even beyond what she pays Federline in child support.

The source says Spears making more money doesn’t change the needs of 12-year-old Sean and 11-year-old Jayden.

The Blast reported on Tuesday that Spears’ father, Jamie Spears – who is the singer’s court-appointed conservator – outlined a monthly budget for Federline as opposed to discussing an increase in child support when the two sides met last week, which left Federline “Insulted.”

“Jamie [Spears] shouldn’t confuse his function of being the conservator for Britney with becoming a conservator for Kevin,” Kaplan tells ET. “He’s the conservator of Britney not the conservator of Kevin. … Kevin wants to be able to provide for the children from the child support he receives, not that Britney buys everything for the kids.”

Spears has been dating boyfriend Sam Asghari for more than a year.