Kelly Clarkson has been forced to cancel the rest of her U.S. tour dates due to vocal problems.

The "Since U Been Gone" singer's doctor has ordered her to remain on vocal rest for the remainder of the year, according to Rolling Stone. As a result, Clarkson was left heartbroken when she had to inform her fans of the cancellations for her "Piece by Piece" tour.

"I can't wait to get healthy and see y'all back on the road soon," she tweeted. "I hate canceling and I am truly sorry to my fans that have been excited to see this show. Please know that I never cancel anything unless it's absolutely necessary."

The singer had previously canceled her Canada and U.K. dates as well. She was scheduled to start her 10-city trek in Canada on Wednesday, Sept. 30. Following these dates she would have played six shows across the pond in November.

"I was so looking forward to sharing this tour with all my amazing fans in Canada and the UK," she wrote in a note to fans on her website. "Unfortunately my doctor is telling me I have to stay on vocal rest, but I am working hard to get better as fast as possible."

Clarkson has had vocal problems for some time now. She told Entertainment Tonight earlier this year that she first lost her voice after the birth of her daughter, River Rose, in June 2014.

"I literally had a moment where I cried and drank wine all day," she said. "I was like, 'Oh, God, I'm not going to be a singer anymore!' I was bawling to my husband and like, completely hammered, just going, 'Oh my God, it's over. I don't know what I'm going to do.'"

The singer released her seventh studio album, "Piece by Piece," on Feb. 27. She announced in August that she's expecting her second child with husband Brandon Blackstock.

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