Michael Douglas and Catherine Zeta-Jones are reportedly on a 'break', Ross and Rachel style.

The couple - who have not been photographed together since April - have decided to separate in order to spend some time apart, although neither Michael nor Catherine have made any movements to file for divorce or legally separate with a source told the new issue of People magazine: 'They're taking a break.'

Douglas is said to be currently on vacation on a yacht off the coast of Sardinia, while Catherine is at home in New York with their two children, Dylan and Carys.

The two stars tied the knot in 2000 at Manhattan's Plaza Hotel, and their relationship was thought to be one of the strongest in Hollywood but their 13-year marriage has come under intense pressure in the last three years with Michael being diagnosed with throat cancer in 2010. Douglas beat the disease and has been cancer-free for two years, but Catherine was diagnosed with bipolar II disorder in 2011 and although she was treated in a mental health facility that year she had to receive more clinic-based treatment in May this year.

These two life-changing things are said to have put a massive strain of the relationship, with a friend of the couple saying: 'The stress has taken a toll on their marriage.'

Just last month Catherine claimed she and Michael were still strong as a couple because they give each other the right amount of space. When asked what the secret to their long-lasting marriage was, she responded: 'Respect, space and a sense of humour. We spend a hell of a lot of time together, so we are careful to maintain our space. We recently had an extension built, to house a closet. I go in there and never come out. My husband knocks on the door and says, 'Can I come in?' But I've got a TV in there, and my daughter brings her friends in - they play shop, put on all my stuff. I could be in there for the whole day, happily.'

Fingers crossed the break does them good and neither of them has to read a letter 18 pages long (front and back).