Turkey's prime minister used his UN General Assembly speech to press demands for a "safe zone" to be created in Syria to protect civilians fleeing barrel bombs and the Islamic State group.
Russia rejected accusations that Moscow had bombed moderate rebel factions fighting President Bashar al-Assad instead of Islamic State fighters and had hit civilians.
The United States does not oppose Russian air strikes in Syria if they target the Islamic State group, but Bashar al-Assad must step down.
US President Barack Obama said that Syrian leader Bashar al-Assad must go if the Islamic State group is to be defeated.
NATO General Philip Breedlove expressed concern Monday about the strength of Russia's military build-up in northwestern Syria and the apparent creation of a defensive "bubble" in the Mediterranean.
France gave cautious backing at the United Nations to a call from Russian President Vladimir Putin for a "broad coalition" to fight the Islamic State group in Syria.
British Prime Minister David Cameron called for discussions on how to bring about political transition in Syria as he prepares to meet world leaders at the United Nations General Assembly.
Iranian President Hassan Rouhani said in an interview that he is ready to discuss a "plan of action" for Syria's post-war future after the Islamic State group is defeated.
Russia has shocked the West by boosting its military presence in Syria as President Vladimir Putin seeks to not just defeat Islamic State radicals but also to gain a firm foothold in the strategic Middle Eastern country.
Kazakhstan is ready to accept refugees from Middle Eastern countries.
The United States and Russia could find ways to cooperate on the crisis in Syria, Pentagon chief Ashton Carter said, as Moscow continues a military build-up in the war-torn nation.
Turkish President Recep Tayyip Erdogan, a fierce critic of Bashar al-Assad, suggested for the first time that the Syrian president could have a role to play in a future political transition.
Israeli Prime Minister Benjamin Netanyahu and Russian President Vladimir Putin have agreed on a plan to avoid "misunderstandings" in Syria.
Russia's military backing for the Syrian regime only risks sending more extremists to the war-torn country and could further hamper any effort at bringing peace.
The White House said it was open to limited talks with Moscow following the controversial deployment of Russian troops and heavy weapons to war-torn Syria.
Russia wants talks with the US military to ensure their forces do not come into conflict as it continues its build-up in Syria, Secretary of State John Kerry said.
French President Francois Hollande, whose country is carrying out surveillance flights over Syria, said it would be "necessary" to carry out air strikes against Islamic State militants there.
President Barack Obama has asked for at least 10,000 Syrian refugees to be admitted to the United States next year, amid criticism his government has done too little to help.
Chancellor Angela Merkel won a hero's welcome as she visited a Berlin migrant centre, with Syrians cheering and taking selfies as Germany threw open its doors to thousands of refugees.
Russian Foreign Minister Sergei Lavrov discussed the Syrian conflict with US Secretary of State John Kerry for the second time in four days.