Olivia Newton-John has opened up about her unbreakable bond with her Grease co-star John Travolta as she paid tribute to his late wife Kelly Preston.
READ: Olivia Newton-John recalls terrifying moment she was diagnosed with breast cancer
During an interview with ET Canada, the 72-year-old - who is battling stage 4 cancer herself - remarked: "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 she was a beautiful human."
Kelly passed away in July, at the age of 57, following a two-year battle with breast cancer.
WATCH: A look back at Kelly Preston's life
Olivia also added: "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."
MORE: John Travolta's daughter posts rare childhood photo with late mum Kelly Preston
READ: Olivia Newton-John and Arnold Schwarzenegger pay heartfelt tribute to Kelly Preston
She starred as Sandy while John played Danny Zuko opposite in the iconic seventies movie, which propelled them into the limelight. Of their friendship, the actress said: "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 ten 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."
© Photo: Getty ImagesOlivia shares a close bond with Grease co-star John Travolta
In 2016, Olivia spoke to People about a dinner date she had with John at his home, where her husband John Easterling watched Grease for the very first time.
"John Travolta invited us to dinner because he wanted to meet my John," she revealed. "He has his plane parked on his own private runway, amazingly."
The actress added: "I told him that John had never seen Grease, so he said, 'Well, why don't we have dessert on the plane?' My John had never seen it, so he got to see it with the two of us. It's hilarious when I think about it. It sounds like a movie, but it really happened!"
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