"There was a request for a donation," Sheen tells syndicated TV show "Entertainment Tonight" in an interview that was to air Tuesday night. "Without getting into it here ... there is a specific document relating to this that I am going to reserve for a court."
When asked if he would ever consider such a possibility, the 41-year-old actor says: "I would sooner, in exactly what I'm wearing, walk on the surface of the moon. Does that answer it?"
A spokeswoman for Richards, 36, wasn't immediately available for comment.
Richards and Sheen divorced last year. He recently filed court papers requesting changes in the custody agreement for the couple's two children, 3-year-old Sam and 2-year-old Lola. He wants an extra weekend a month, permission to hire his own choice of child care provider, and an order that when he's got the kids, Richards can only call him in case of emergency.
"The thing I'm most excited about is my recent engagement," he says. "She's just easy and loving and smart, and if everybody was just as happy to see me when I walk through a door as her, my life would be perfect."
The interview was posted on etonline.com.