The Russian and US presidents started their discussion on Monday on the sidelines of the G8 summit in Northern Ireland set to focus on the Syrian crisis.
The US said last week that it would back the rebel forces because it had “high confidence” that the Syrian government used chemical weapons in the conflict. That claim was supported by Britain but dismissed as “unconvincing” by Russia on Friday.
Vladimir Putin and Barack Obama are also expected to discuss preparation for the upcoming international conference on Syria proposed earlier by Russia and the United States to end Syria’s two-year-old civil war.
The Russian and US leaders will also talk the planned US troop withdrawal from Afghanistan in 2014 and missile defense, which remains a sticking point in bilateral ties.
The Russian delegation at talks includes Foreign Minister Sergei Lavrov and Russian presidential aide Yury Ushakov. The US delegation includes National Security Advisor Tom Donilon and Alice Wells, senior director for Russia and Eurasian Affairs at the National Security Council.