President Obama: 'Not there yet' on US, Russia deal on Syria violence

His comments came as John Kerry and Sergey Lavrov are in talks over a deal to boost US and Russian military cooperation to fight the IS

The United States and Russia are working "around the clock" to try to strike a deal to reduce violence and improve access to humanitarian help in Syria, President Barack Obama said on Sunday, but added that the US was skeptical it would work.

Obama, speaking on the sidelines of the Group of 20 economic summit in China, said the US and Russia still have "grave differences" about what's needed to end Syria's civil war and which opposition groups are legitimate targets for the US and Russian militaries. But he said "it is worth trying" to secure an agreement nonetheless.

"We're not there yet," Obama said. "I think it's premature for us to say there's a clear path forward, but there's the possibility at least for us to make some progress."

Obama's comments came as US Secretary of State John Kerry and Russian Foreign Minister Sergey Lavrov are deep in talks over a deal to boost US and Russian military cooperation to fight the Islamic State group and other extremists in Syria a step Moscow has long sought.

The emerging deal is expected to also include provisions to ensure aid can reach besieged areas of Syria and steps to prevent Syrian President Bashar Assad's government from bombing areas where US-backed rebels are operating.

Though negotiators have been hopeful a deal could come together while world leaders are gathered in Hangzhou for the G20, that optimism has been tempered by the failure of previous ceasefire deals to hold.

The US has long been wary of increasing military coordination with Russia in Syria's civil war because it says Russia continues striking moderate, US-backed opposition groups in a bid to prop up Assad. The US Wants Russia to focus exclusively on IS and al-Qaeda-linked groups.

"These are difficult negotiations," Obama said. He added later: "If we do not get some buy-in from the Russians on reducing the violence and easing the humanitarian crisis, then it's difficult to see how we get to the next phase."

Discussions about the intractable Syria conflict and the related fight against IS have been a major focus as world leaders gather for the G20, which brings together the world's major economies.

Obama, who met first with new British Prime Minister Theresa May, also planned to discuss Syria when he meets with Turkish President Recep Tayyip Erdogan, their first sit-down since the summer's failed coup in Turkey.