She underwent the surgery, described as "minimally invasive", on Wednesday in Los Angeles, and will now have radiation therapy.

"Her doctors think her prognosis is excellent, " said her publicist, but she has had to postpone her North American tour scheduled to begin next month.

Three weeks ago she separated from her fiance, cyclist Lance Armstrong, who himself has overcome cancer. On her website, Crow, 44, said she had benefited from early detection of her condition, and encouraged other women to have regular check-ups.

"Approximately one in seven American women will be diagnosed with breast cancer in her lifetime and more than two million Americans are living with breast cancer today, " Crow said, adding: "I am joining the more than 200,000 women who will be diagnosed with breast cancer this year."

It is not known when she was diagnosed with the disease.

Her former fiance, seventime Tour de France winner Lance Armstrong, survived testicular cancer.

"Once again I'm reminded of just how pervasive this illness is, as it has now touched someone I love deeply, " said Armstrong.