Olivia Newton-John says John Travolta's late wife Kelly Preston was a "beautiful human", and praised the pair for being "dear friends".

Olivia Newton-John

Olivia Newton-John

The 'Grease' actress has paid tribute to her co-star's significant other Kelly, who died in July aged 57 after a secret two-year battle with breast cancer, and she is auctioning some of her personal items to raise money for her Olivia Newton-John Foundation, which funds the discovery of kinder cancer therapies.

Olivia - who is battling the disease for a third time - said: "You know, John and Kelly chose to keep her illness secret and private and I want to honour that and just say they are dear friends and I really you know, she was a beautiful human.

"I’ve lost way too many friends to cancer and you know, I’m on that journey myself, so I’m powerfully driven to find kinder answers for treatments for cancer, prevention, and treatments."

Olivia starred alongside John in 1978 cult musical movie 'Grease', and every 10 years she thinks people's love of the motion picture will "fade away", only for the film to get "bigger and bigger".

She added to 'ET Canada': "[John]’s a dear friend and he always will be and you know Didi [Conn], also.

"We formed great bonds making that film as you can imagine and it’s always amazing to me that every … it’s 40 years now and every 10 years I thought … it’s going to fade away now but it just gets bigger and bigger and it seems to find a younger audience all the time it’s really quite amazing."

Olivia previously paid tribute to Kelly following her death, describing her as a "loving, devoted wife, mother and sweet friend".

She said: "Kelly was a radiant, warm and gentle spirit - a loving, devoted wife, mother and sweet friend.

"My heart breaks for John, Ella and Ben. No words can express my sorrow for her family.

"Kelly's light shines on in her beautiful children."