The iconic vocalist made the announcement on Instagram Friday, expressing "tremendous disappointment" she would be unable to continue her sold-out tour. But, she insisted she's "working really hard to build back her strength" while pointing out it's hard to tour even when you're feeling 100 percent.

Celine also apologized to her fans for disappointing them and acknowledged it was unfair to keep postponing shows. This time around Celine canceled performances in France, Belgium, Denmark, Poland and the UK.

She ended with this ... "I want you all to know, I'm not giving up … and I can't wait to see you again!"

As you know, Celine previously postponed concerts after publicly disclosing in December she was suffering from stiff-person syndrome. SPS is a rare neurological disorder that causes stiffness in the torso, arms and legs, and creates emotional distress and muscle spasms.

After Celine broke the bad news, she received some good news from her fans on social media.

One fan wrote: "We love you Celine, take good care of yourself, your health is the most important and precious thing. We are praying for your healing."