U.S. Secretary of State John Kerry has opened a second day of talks in Geneva aimed at finding a way to restore at least a partial truce in Syria amid continuing attacks in Aleppo.

Kerry met on Monday with Saudi Foreign Minister Adel al-Jubeir and planned to meet later with the U.N. envoy for Syria, Staffan de Mistura. Kerry said progress was being made toward an understanding on how to reduce the violence in Aleppo but that more work was needed.

Al-Jubeir called the situation in Aleppo an "outrage" and a criminal violation of humanitarian law. He said that Syrian President Bashar Assad would be held accountable for the attacks and would be removed from power either through a political process or by force.