US Secretary of State John Kerry say he and Russian Foreign Minister Sergey Lavrov have made significant headway on Syria, although minor details of a planned truce in the war-torn country still have to be discussed.  The two have held marathon talks in Geneva. 

"We have completed the vast majority of those technical discussions which were primarily focussed on making this cessation real, and improving the level of humanitarian assistance and thereby getting the parties to the table so we can have a serious negotiation about how to end this war," said John Kerry.

"We're not talking about how to stop the air forces, but how to make the air strikes more efficient, so that we can better fight the extremist groups and terrorism," said Sergey Lavrov.

Kerry says among the details that still need to be finalized are how to ensure the Syrian army follows the truce, as well as the logistics for relief efforts in besieged areas. Lavrov says progress was made during the meetings. He says his side's most pressing concern is how to distinguish US-backed anti-government fighters from terrorist groups. The two diplomats say experts from both their countries will work on the details in Geneva in the coming days.