Michael Douglas and Catherine Zeta-Jones Separate

People Exclusive

08/28/2013 at 07:30 AM EDT

Michael Douglas and Catherine Zeta-Jones

Michael Douglas and Catherine Zeta-Jones haven't been photographed together since April 22. They've walked red carpets solo, vacationed separately with their kids, and in recent days, Douglas has been relaxing on a yacht off the coast of Sardinia – with Zeta-Jones at home in New York.

So what's really going on with one of Hollywood's most celebrated couples? In this week's new cover story, two close confidantes tell PEOPLE that they've decided to take time apart: "They're taking a break," one source says.

Neither star has filed for divorce or moved toward a legal separation, sources say.

The A-list pair, who wed in 2000 in a lavish celebration at Manhattan's Plaza Hotel, have faced more than their fair share of ups and downs over the last three years – between Douglas's 2010 cancer battle and Zeta-Jones's struggles with bipolar II disorder. “The stress has taken a toll on their marriage,” a friend tells PEOPLE.

Douglas, 68, and Zeta-Jones, 43, who have two children, Dylan, 13, and Carys, 10, together, decided to spend time apart soon after he came back from the Cannes Film Festival in May. Zeta-Jones had recently returned from a scheduled second round of treatment to monitor her bipolar disorder.

Those close to the couple hold out hope they can work out their differences. Says one family friend: "They want the best for their kids, no matter what happens."

For more inside details of their relationship and the strains that led them to separate, pick up this week's issue of PEOPLE, on newsstands Friday