United States pop singer Anastacia has been diagnosed with breast cancer.

The 29-year-old was diagnosed with the disease at the weekend and is set to have surgery to remove a lump.

But she has vowed to work through the illness and doctors have caught the disease in its early stages.

I'm a fighter by nature and nothing will ever change that. Anastacia

The star, whose hits include I'm Outta Love, also suffers from the bowel condition Crohn's disease and underwent an operation at the age of 13 for the illness.

She said: "My doctor was insistent that I have a mammogram (during a routine check-up last week) even though it was not required. He saved my life.

"I appreciate all who are concerned, but please don't worry. Either way I have no intention of letting this news get me down.

"I'm a fighter by nature and nothing will ever change that."

Gary Farrow, UK vice president of her record label Sony, told The Sun newspaper that it was "business as usual" for the star and she would be fulfilling her work commitments, including shooting a video for her next single.

The head of UK breast cancer charity Breakthough Breast Cancer said developing the condition at Anastacia's age was highly unlikely.

"For someone so young to be diagnosed with breast cancer is very rare. Around two per cent of the 39,000 breast cancers diagnosed every year in the UK occur in women under the age of 35.

"The vast majority of breast cancers - around 80 per cent - occur post-menopausal women over the age of 50.

"Anastasia's breast cancer was found early and this underlines the importance of all women being 'breast aware', said Delyth Morgan, chief executive of Breakthrough

Anastacia found fame after her strong voice ensured fans took notice of her music.

Hard to market

But it took many years for record companies to notice her talent, with many believing her distinctive sound would be too hard to market.

She was finally signed after Sony bosses saw her on MTV's The Cut.

She has since released two albums, Not That Kind and Freak of Nature.

Her single Boom! was chosen as a World Cup anthem in 2002, which she performed at the closing ceremony in Japan.

The Chicago film soundtrack also features a track from Anastacia, Love is a Crime - a song inspired by the musical.