A statement released by Zeta-Jones' publicist said the couple are "taking some time apart to evaluate and work on their marriage".
A source also confirmed to People magazine that they are 'on a break', but neither has filed for divorce or moved toward a legal separation.
Rumours about Catherine and Michael's 13-year marriage have been circulating for a few weeks, as they haven't been pictured together since April, and have recently taken separate holidays with their two children.
They married in 2000 in a lavish ceremony at Manhattan's Plaza Hotel in New York, and are parents to 13-year-old Dylan and 10-year-old Carys.
According the to the magazine, friends close to the couple are hoping they can work things out for their children's sake.
"They want the best for their kids, no matter what happens," they said.
Their marriage had weathered Michael's battle with throat cancer, and Catherine's bipolar disorder.
The 'Chicago' star only recently returned home from rehab for a scheduled second round of treatment.