Singing great Olivia Newton-John revealed Tuesday a return of breast cancer, 25 years after her first successful battle made her an advocate for fighting the disease.

The British-born star said she was obliged to postpone a tour of the United States and Canada following her new diagnosis.

The 68-year-old said she will undergo a short course of radiation, as well as natural therapies, upon the advice of specialists at a cancer research center named after her in her adopted home of Melbourne, Australia.

The singer "is confident she will be back later in the year, better than ever, to celebrate her shows," said a statement by her management.

Newton-John has been a chart-topper since the 1970s with songs that stretch into pop, folk and country but she became best-known for starring in the 1978 musical comedy "Grease" alongside John Travolta.

Newton-John was first diagnosed with breast cancer in 1992, forcing her to halt her schedule.

The experience had a major impact on Newton-John who became an advocate for research into cancer and for early detection.

She has dedicated a series of albums and concerts to cancer and other charities and raised funds to build the health center in Melbourne.

Newton-John had earlier postponed the first half of a North American tour complaining of back pain.

After consulting doctors, she learned that the pain was connected with breast cancer which had spread to the sacrum bone of her back.