After years of asking longtime companion Farrah Fawcett to marry him, actor Ryan O'Neal says she has finally agreed, even as she nears the end of her life after a long battle with cancer.

"I've asked her to marry me, again, and she's agreed," O'Neal says in an interview with Barbara Walters for ABC television show "20/20" to air on Friday, according to publicists for the show.

O'Neal spoke to Walters as 62-year-old Fawcett, the former star of the 1970s TV show "Charlie's Angels," struggles for survival after being diagnosed with anal cancer in 2006, which has now spread to her liver.

O'Neal, 68, who has dated Fawcett on and off since the early 1980s, told Walters she is "fighting for her life" but will "absolutely" get married.

"We will, as soon as she can, say yes . . . maybe we can just nod her head," he told Walters.