Olivia Newton-John is suffering from ''very painful'' sciatica.

The 68-year-old singer was recently forced to postpone some of her shows on her 'Liv On' tour after falling ill, and the star has now revealed she has been battling a ''long running issue'' with the chronic condition which is caused by irritation or compression of the sciatic nerve.

Writing on Facebook over the weekend, Olivia told her fans: ''Hi everyone! I was so sad to have to postpone some shows this month, and to my fans who planned on coming to my concerts please know I am disappointed too! We are rescheduling as soon as possible.

''I have had a long running issue with sciatica and I need to take this time to rest and deal with this very painful condition .
My husband John is taking great care of me and I want to thank all my family, friends and fans for their concern, love, support and good wishes.

''I look forward to returning to performing soon!

''Love and light,
''Olivia x (sic)''

It isn't the only health scare the 'Grease' star has had either, as over two decades ago she was diagnosed with breast cancer, and recently admitted she was ''grateful'' for the experience because it ''taught her compassion''.

She said: ''I am grateful for the experience because without it I would not have done many of the things I have done in my life. It's taught me compassion for those going through difficult times.''

Meanwhile, Olivia - who has 31-year-old daughter Chloe with her ex-husband Matt Lattanzi - previously admitted she never felt better after having a mastectomy.

Speaking about her feelings towards the procedure, she shared: ''I felt complete and utter dread. One night, shortly after it had been confirmed that I needed a mastectomy, I couldn't sleep. I went downstairs, sat in the dark and felt the fear washing over me. I was convinced that the cancer had spread at top speed and was in every part of my body.

''For a few weeks my world was in turmoil, but then I calmed down and started to fight back mentally. Deep down, there was always a tiny nugget of hope inside me that said, 'You'll be OK. You'll make it,' and that little voice kept me going.''