A member of the U.N. Commission of Inquiry on Syria said on Sunday she was quitting because a lack of political backing from the U.N. Security Council had made the job impossible, Swiss national news agency SDA reported.

Carla del Ponte, 70, who prosecuted war crimes in Rwanda and former Yugoslavia, told a panel discussion on the sidelines of the Locarno Film Festival that she had already prepared her letter of resignation.

"I am quitting this commission, which is not backed by any political will," she said, adding that her role was just an "alibi.