The UN Secretary-General Ban Ki-Moon has for the first time is called for the situation in Syria to be referred to the International Criminal Court.
In his state of the world address to leaders from the UN's 193 member states, Mr Ban said “innocent Syrians pay the price of more barrel bombs and terrorism” and there must be no impunity for “atrocious” crimes.
The Associated Press said his call opened the annual General Assembly gathering of world leaders that includes addresses from President Barack Obama, Russian President Vladimir Putin and Chinese President Xi Jinping.
Just seen the full text of David Cameron's #Syria speech: Send Assad to the ICC—but only after we work with him as a partner in transition!— Kyle W. Orton (@KyleWOrton) September 27, 2015
Mr Ban says five countries “hold the key” to a political solution to Syria: Russia, the US, Saudi Arabia, Turkey and Iran.
The UN chief said the Syrian conflict is “driven by regional powers and rivalries.”
His remarks followed a weekend in which Russia appeared to seize the initiative in international efforts to end the conflict in Syria, with Washington scrambling to devise a new strategy and France sending warplanes to bomb Islamic State targets.
US Secretary of State John Kerry discussed Syria with Russian Foreign Minister Sergei Lavrov. He said that while it was vital to coordinate efforts against Islamic State militants this was not yet happening.
“I think we have concerns about how we are going to go forward,“ Mr Kerry told reporters. US officials said Kerry was working on a new political initiative in New York that would include Russia and key regional powers.
But Reuters said that it was announced in Baghdad that Russian military officials were working with counterparts from Iran, Syria and Iraq on intelligence and security cooperation to counter Isis.
Russian President Vladimir Putin derided US efforts to end the Syria war, which has driven a tide of refugees into neighboring states and Europe.
He said Moscow, which this month sent tanks and warplanes to a Russian military base in Syria, was itself trying to create a “coordinated framework” to resolve the conflict.
“We would welcome a common platform for collective action against the terrorists,” Mr Putin said in an interview on Sunday with CBS.Reuse content