Veteran actress Valerie Harper is refusing to accept her brain cancer diagnosis as a "death sentence" and is "more than hopeful" she will overcome her latest battle against the disease.

The former Mary Tyler Moore Show star, 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.

Harper admits the seriousness of her health crisis only hit her when she realised there was no cure for leptomeningeal carcinomatosis, a condition that occurs when cancer cells spread into the fluid-filled membrane surrounding the brain.

She tells U.S. breakfast show Today, "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 (sic) have lived much longer than the prognosis.'"

The 73 year old has even taken to talking to her cancer cells in a bid to stay alive: "I talk to them, I do. I say, 'Listen to me little guys. You can live if you don't kill me.' Why not?"

Harper, who went public with her health battle earlier this month (Mar13), has surprised her fans and friends with her bright demeanour and positive attitude towards her future and she insists on continuing to live her life as normally as possible.

She says, "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... (I'm) more than hopeful... I have an intention to live each day fully."

However, there is one prospect which brings her to tears - the thought of never seeing her husband Tony Cacciotti's face again.

She adds, "He's a gorgeous guy. I always knew that, it was part of falling in love with him. He's wonderful."