The actress and activist Jane Fonda says she "worries" about climate activist Greta Thunberg.
"She understands that if she's attacked it's because she's making a difference and that scares people," says Fonda.
The 81-year-old has vowed to protest every Friday until January to demand for action to be taken to address climate change.
Thunberg, 16, found fame after her youth climate strike protests spread to schools around the world.
"They handcuff you with plastic things, not the old good metal ones. They hurt more," Fonda says of her most recent arrest.
But she says: "I don't want to go to prison.
"I don't think that Jane Fonda the martyr is exactly what the movement needs right now."
"The police are figuring out what to do. I was told if I keep getting arrested every week I may be put in the slammer. I may not get arrested every week because I have to start filming Grace and Frankie (her series for Netflix)."
Fonda has been an active campaigner for years, being involved in Native American rights campaigns, civil rights campaigns and protesting against the Vietnam War.
"I haven't been very well in my skin because I knew I wasn't doing what I can do. I was not a super happy person until I started to do this."
She says she asked an "ocean scientist" taking part in her recent protest, "How do you stop from getting depressed?
"He said, 'I become active. The minute you start doing something about it, the depression goes away'."
Her latest action, she says, was inspired by the student protests led by Thunberg.
They are "more politically savvy than we ever were at that age. They're much more sensitive of diversity. This can't be a white, elite climate action.
You can hear the full interview with Jane Fonda on BBC Radio 4's Broadcasting House.