GENEVA—Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov said they have agreed on the majority of technical steps necessary to implement a deal to reach a nationwide cease-fire in Syria that would include closer military cooperation between the two countries.

Messrs. Kerry and Lavrov were short on specifics when they spoke to reporters Friday evening after more than nine hours of on-and-off talks.

“We achieved clarity on the path forward,” Mr. Kerry said. He added that the sides have completed the vast majority of technical discussions, though Mr. Lavrov said Russia was still concerned about the commingling of terrorist groups with rebel fighters.

Mr. Kerry said technical teams from both sides would pursue the details of an agreement in Geneva in the coming days.

It was unclear after Friday’s meeting if the deal Mr. Kerry proposed in Moscow in July, which would include Russia grounding Syrian President Bashar al-Assad’s air force in exchange for closer coordination against the Syria Conquest Front, formerly the al Qaeda-linked Nusra Front, will ever come to fruition.