Any agreement between the US and Russia to expand military or intelligence cooperation in Syria would depend entirely on Moscow's support for the US goal there to ensure operational security, and that it would not be based on trust, Pentagon officials have said.

The Obama administration reportedly remained divided over deepening cooperation with Russia to combat Islamic State (Isis) militants. US Secretary of State John Kerry said on 22 July that he would meet his Russian counterpart in the coming days to strike a deal for closer cooperation.

Military and intelligence officials in the Pentagon have raised doubts over Russia's trustworthiness, expressing fears that US intelligence sources and military methods could be exposed.

Marine General and Chairman of the Joint Chiefs of Staff Joseph Dunford told reporters: "We're not entering into a transaction that's founded on trust. There will be specific procedures and processes in any transaction we might have with the Russians that would account for protecting our operational security," Reuters reported.

The cooperation is expected to establish new ways of sharing intelligence on the whereabouts of jihadists in Syria's multi-sided war. Washington will also reportedly seek Russia's assurance that President Bashar al-Assad's troops would stop attacking moderate rebels backed by the US.

Defence Secretary Ashton Carter said Kerry's negotiations with his Russian counterpart are based on "mutual interest to the extent and when and as we are able to identify that with the Russians".

If a deal is reached, it could deepen cooperation between the US and Russia in the conflict-ravaged region as well as breathe new life into the February ceasefire that has remained in tatters.

Kerry is expected to meet Russian Foreign Minister Sergei Lavrov on Tuesday (26 July) on the sidelines of the Asean summit in the Laotian capital of Vientiane.

Pentagon on Russia deal in Syria
Secretary of Defense Ashton Carter, (L), and Chairman of the Joint Chiefs of Staff General Joseph F Dunford speak to the media at a news conference in the Pentagon on 25 July 2016. They said the proposed agreement with Russia is 'not based on trust' Mark Wilson/Getty Images