Tito Ortiz is doubling down on his Chuck Liddell call-out ... telling TMZ Sports straight-up that he's down for a 3rd fight with the Iceman!
"I don't need to fight, but if Chuck needs to ... I'll be a good friend like he was once and give him a payday," Ortiz said ... adding that ONLY Chuck could pull him outta retirement.
The bad news -- Tito says he proposed Ortiz vs. Liddell 3 to a UFC matchmaker on New Year's ... and got shot down HARD 'cause they're worried about Chuck's health.
"He kinda looked at me and laughed and said, 'Chuck couldn't fight again! He's been knocked out unconscious 5 times! I guarantee you the doctor won't give him a license."
But that ain't stoppin' Chuck -- who tells us he's still training his ass off.