Canadian pop singer Celine Dion announced on Friday that she was canceling the European stretch of her world tour, scheduled to resume this summer, due to a medical condition that makes it difficult for her to perform.

The announcement comes four months after the 55-year-old Quebecoise singer said she was diagnosed with a rare neurological disorder called stiff-person syndrome that causes muscle spasms. At the time, the disorder forced her to postpone some European shows on her "Courage World Tour."

"I'm so sorry to disappoint all of you once again," the singer - best known for the "Titanic" movie theme song "My Heart Will Go On" - wrote on Instagram on Friday morning.

"I'm working really hard to build back my strength, but touring can be very difficult even when you're 100%."

The tour's European stretch consisted of 42 shows in seven cities from late August to early October and another 17 cities during the spring of 2024. Dion said ticket holders would receive refunds.

Stiff-person syndrome causes muscle rigidity and increased sensitivity to sound, touch and emotional stimuli that can trigger spasms. The condition led the multiple Grammy winner to postpone her Las Vegas residency in October 2021.

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The tour - her first in the United States in 10 years - kicked off in Quebec City in September 2019. It was accompanied by the release of her latest album "Courage."

The singer said the album's title was inspired by the 2016 death from throat cancer of her husband and manager Rene Angelil. The couple had three children.