Valerie Harper, who starred in classic US sitcoms The Mary Tyler Moore Show and spin-off series, Rhoda, says she is refusing to accept her brain cancer diagnosis as a "death sentence."

The 73-year-old who previously survived a tumour in her lung, has been warned she could have just three months to live after learning she has a rare form of terminal brain cancer, but she is determined to put up a fight until the very end.

Speaking to US breakfast show Today, she said: "Incurable's a tough word. So is 'terminal'. But he (the doctor) then said, 'It could be a week, you could have a seizure; it could be three months, it could be several years.

"I have people with this disease that have lived much longer than the prognosis.'"

Harper, who went public with her health battle earlier this month, added: "A lot of folks were calling, 'Can I come by the house? Are you in a wheelchair?' because they hear it (cancer) as this death sentence, which it may well be but I'm not dying 'til I do. I promise I won't.”