OLIVIA NEWTON-JOHN is training hard for a walk to raise funds for a cancer research hospital in her name. But this walk is no ordinary fundraiser -- Olivia will trek along the Great Wall of China for 21 days!

"The walk on the Great Wall symbolizes the cancer journey," she tells ET. "It's long and arduous, but we'll triumph in the end."

Cancer survivor LEEZA GIBBONS, JOAN RIVERS and former "Party of Five" star SCOTT WOLF are among the celebs joining Olivia on the extreme challenge starting April 7, and Olivia's been working out at Curves, a sponsor of the walk, to get ready.

"I want to do it for my hospital, but now it's a challenge for me personally to do this," the singer says of the Olivia Newton-John Cancer and Wellness Centre in Australia.

Olivia has also recorded a duet with Chinese pop star SUN HO for a CD called Great Walk to Beijing: A Celebration in Song, which includes duets with KEITH URBAN, RICHARD MARX, BARRY GIBB and others, all to raise funds for the hospital.

A breast cancer survivor herself, Olivia tells ET that her thoughts are with PATRICK SWAYZE, who is currently battling pancreatic cancer.

"I spent some time with Patrick and his horses," says Olivia. "We rode his beautiful Arab horses together -- I'll send him a personal message, but I'd just like to send my love right now."

For more information in the walk and the hospital, visit www.greatwalktobeijing.com and www.oliviaappeal.com.