The United States says reports of Russian airstrikes killing hundreds of Syrian civilians are "extremely disturbing" and that attacks on the country's most vulnerable people undermine efforts to bring a political resolution to the country's conflict.
State Department spokesman Mark Toner said Tuesday there is a focus on pushing the political process ahead of planned peace talks next month and that all parties with a stake in Syria need to be working on confidence-building measures.
Human rights groups have reported Russian airstrikes hitting civilian targets, adding to the criticisms from Western governments that Russia's campaign has bolstered Syrian President Bashar al-Assad instead of targeting Islamic State militants.
"We have at times in the past six months to a year seen Russia play a more positive or constructive role on the political side of resolving the Syrian conflict," Toner said. "We'd like to see that now manifested on the kinetic side, if you will."
He said Secretary of State John Kerry discussed concerns about the strikes in a phone call with Russian Foreign Minister Sergei Lavrov.
"We've consistently urges all sides of the conflict to take all feasible precautions to reduce the risk of harming civilians and comply with their obligations under international humanitarian law," said Toner.
Russia has denied the allegations about its military campaign in Syria, which began in late September.
Toner said that while it is not clear whether Russia or Syria was responsible for an airstrike last week that killed Zahran Alloush, the head of an opposition group called Jaysh al Islam, his death complicates the peace effort.
"We do know that Russia has been supporting the regime through its military strikes, so regardless, whether it was the regime, whether it was Russia that carried out those strikes, Russia has helped enable the regime to carry out more aggressive airstrikes on some of these opposition groups," he said.
Toner said Kerry highlighted in his conversation with Lavrov that there is a peace process and those backing the process need the opposition groups who want to participate to know they will not be targeted.
U.N. envoy for Syria Staffan de Mistura wants to bring what he called the "broadest possible spectrum" to Geneva for negotiations beginning January 25.
Two previous rounds of U.N.-brokered talks ended early last year with little progress.