The Russian Orthodox Church has called for members of the Pussy Riot punk band to repent, on the eve of an appeal court ruling on their two-year prison sentences for performing an anti-Kremlin song in Moscow's main cathedral.

The three performers of the "punk prayer" criticising President Vladimir Putin's close ties with the Russian Orthodox Church were convicted of "hooliganism motivated by religious hatred" by a district court on August 17.

Vladimir Legoida, a senior church spokesperson, said on Sunday their act "must not remain unpunished whatever the justification," but that any repentance, if expressed, should be taken into account.

"The church sincerely wishes for the repentance of those who desecrated a holy place, certainly it would benefit their souls," Legoida said in an official address.

"If any words of the convicts indicate repentance ... we would wish that they are not left unnoticed and those who violated the law get a chance to mend their ways."

A church statement after the August verdict indicated that the clergy would back a pardon or a reduced sentence, but that would have required Nadezhda Tolokonnikova, 22, Maria Alyokhina, 24, and Yekaterina Samutsevich, 30, to admit their guilt, something their lawyers say they will not do.

"If they (the church) mean repentance in the sense of a crime ... it definitely won't happen. Our clients won't admit guilt. A call for that is pointless," lawyer Mark Feigin told independent television channel Dozhd on Sunday.

The trio's legal team and relatives hold out little hope that the sentences - which they believe are excessively harsh - will be quashed or reduced at the hearing scheduled for Monday, whether they repent or not.

"The sentence is predetermined; their repentance will not affect it in any way," Stanislav Samutsevich, father of one of the jailed women, told Reuters.

"The fact the church is calling for that is nothing but a public relations move to sustain their reputation in the eyes of the public, as the church says it is separate from the state."

Patriarch Kirill, the head of the Russian Orthodox Church, has called Putin's 12-year rule a "miracle of God" and backed his presidential election campaign this year.

Kirill dismissed criticism of his backing for the Kremlin on Friday, telling students that close ties between the church and state helped protect and develop society.

The trial exposed Putin to international criticism because of doubts over the independence of the judiciary, and global celebrities including British musician Paul McCartney and US pop singer Madonna called for leniency.