Britney Spears and Kevin Federline
Owen Beiny/WENN; Ethan Miller/Getty
was unable to attend her court-ordered deposition Wednesday morning due to an illness, a lawyer for Kevin Federline
"I was told of a general [medical] condition, and [Spears] felt she couldn't attend," Mark Vincent Kaplan said outside his Los Angeles office.
Spears's friend Sam Lufti tells PEOPLE in an e-mail: "She's sick, both physically and high anxiety. Millions of press outside. It's too much."
A new date was selected, but not revealed. Federline's attorney indicated he "will pursue" a court sanction against the pop star for failing to show.
Spears's testimony was expected to last no more than a day. The pop star, 26, is battling ex-husband Federline, 29, over custody of sons Preston, 2 and Jayden, 1. Federline currently has primary physical custody, with supervised visitation for Spears.
Kaplan already has completed a number of depositions of former Spears associates, including pal Alli Sims, former manager Larry Rudolph, and former bodyguard Daimon Shippen. He'll use evidence gathered in the depositions to argue that Federline should be granted primary custody in the court's final ruling.
On Oct. 26, a court forbid Spears's deposition from being videotaped
. At that hearing, Kaplan complained that Spears had evaded a deposition four times over the course of a year.