Farrah Fawcett and Ryan O'Neal to Marry

June 22, 2009— -- In an exclusive interview with Barbara Walters for "20/20," Farrah Fawcett's longtime love Ryan O'Neal said the couple has plans to marry.

"I've asked her to marry me, again, and she's agreed," O'Neal, 68, told Walters.

O'Neal described Fawcett's deteriorating condition, saying the 62-year-old iconic actress is "fighting for her life.

"We will, as soon as she can, say yes. ... Maybe we can just nod her head," he said, with a laugh.

Fawcett and O'Neal began dating in 1980 and lived together with son Redmond. The two never officially tied the knot, but not for O'Neal's lack of trying.

"I used to ask her to marry me all the time," he said. "But ... it just got to be a joke, you know. We just joked about it."

But O'Neal told Walters that he was confident the two will finally get married. "I promise you, we will. ... Absolutely."

O'Neal also said he has his wedding outfit prepared, telling of the couples' ability to make each other laugh.

As for how he will dress for the ceremony, O'Neal said, "Like a gigolo. You know? And a little thin mustache and slicked-back hair. I don't know. We have fun, we tease about that."

Barbara Walters' complete interview with Ryan O'Neal, as well as Farrah Fawcett's doctor and others who are closest to her, will air on "20/20" Thursday at 10 p.m. ET.