The three women— all members of the Pussy Riot band—were arrested after their February stunt at Moscow's main Christ the Savior cathedral two weeks before March's presidential vote, in which they asked Mother Mary to deliver Russia from Putin's third presidential term.
Nadezhda Tolokonnikova, 23, Maria Alekhina, 24, and Yekaterina Samutsevich, 29 face up to seven years if convicted on hooliganism charges. Their prosecution has caused public outcry and protests from rights groups.
The case has been seen as part of a widening crackdown on dissent that followed Putin's election.
They said in a letter posted on Ekho Moskvy radio's website Wednesday that what some see as their "insolence and impudence" is merely a sarcastic response to a lack of justice.
"We are joyful to hear about those who support us in our trial, and we don't understand the toughness and rudeness of opponents," they said. "We aren't supporters of violence, and we don't bear a grudge against anyone. Our laughter is mixed with tears, and our sarcasm is a reaction to abuse of law."
Amnesty International has said that it considers the three women to be prisoners of conscience "detained solely for the peaceful expression of their beliefs.
Suzanne Nossel, executive director of Amnesty International USA, said in a statement released by the organization Wednesday that the three women are musicians, not hooligans.
"President Putin and his cronies need to stop repressing freedom of speech in Russia and allow these women to return to their families. It's time for Russian authorities to respect the rights of journalists, human rights defenders, musicians, bloggers and ordinary citizens to express themselves."
Amnesty said that Sting, on a concert tour in Russia this week, has also condemned the treatment of the three rockers