Douglas, 68, and 43-year-old Catherine married in 2000, and have two children- 13-year-old Dylan and 10-year-old Carys.
However a source close to the couple has now told a US newspaper:
'They're taking a break.'
This comes after Michael was spotted holidaying alone in Sardinia, while Catherine remains in New York.
The Traffic stars have not been spotted together since April, when they made an appearance on the red carpet at the 40th Annual Chaplin Award Gala at Avery Fisher Hall in New York City.
But they reportedly decided to take a trial break when Douglas returned from the Cannes Film Festival this year.
While it was recently reported in the American press that Catherine was due to begin a $300m divorce battle against Michael, his representatives denied the allegation.
Reports then surfaced suggesting that Michael’s cancer battle, Catherine’s fight with depression, and Michael’s older son Cameron (from his previous marriage) being arrested for drugs offences put strain on their marriage.
Michael is said to be living in Manhattan while Catherine is staying at their $4m home in New York with their children.