The Obama administration reportedly remains divided in its views on whether to rely on Moscow for deeper cooperation in its offensive against Islamic State (Isis) in Syria. US Secretary of State John Kerry is arriving in Moscow on Thursday (14 July) to push for an agreement with Russian President Vladimir Putin that could change the fate of the nearly six-year-old civil war in the Arab nation.

Kerry will meet Putin and Russian Foreign Minister Sergei Lavrov and offer to share military information in a bid to defeat Isis extremists in Syria and Iraq, and the al-Qaeda associate al-Nusra Front, who are also posing a threat in the region's multi-sided war. Kerry will also seek an assurance from Russia, which backs President Bashar al-Assad's regime, to stop bombing moderate rebels backed by the US.

The US has faced criticism that it has no strategy to deal with the challenges posed by Russia in Europe and Syria. "It isn't clear why the secretary of state thinks he can enlist the Russians to support the administration's goals in Syria," one US intelligence official told Reuters.

"He's ignoring the fact that the Russians and their Syrian allies have made no distinction between bombing Isis and killing members of the moderate opposition, including some people that we've trained," the official said. He also questioned the US's decision to share military information with Russia.

Moscow does not want to let go of Assad, and in case he has to step down it would like someone "acceptable to them in power", a defence official told Reuters on the condition of anonymity. "The [US] president has said that Assad has got to go, and our allies, especially the Saudis, hold that view very strongly. In fact, they keep asking us why we're cosying up to Moscow," he added.

Kerry's trip will see the two countries trying to revive an agreement signed in February to cease hostilities, and to get Russia's "buy-in on a process that can lead to a nationwide ceasefire", US State Department spokesman Mark Toner reportedly said.

"We haven't seen that thus far, but we're having another go at this," the Associated Press quoted him as saying.

Besides Syria, the two leaders are also expected to talk about Russia's alleged seizure of the Crimean peninsula and other bilateral issues.

The talks in Moscow come ahead of a deadline set at the Geneva peace talks for diplomatic progress by 1 August. However, a breakthrough seems bleak in Syria as fighting has been intensifying near Aleppo and Idlib, even as Assad's troops gain control of more areas in the region compared to before.

Meanwhile, the delivery of humanitarian aid to the beleaguered areas has been either insufficient or blocked, increasing civilian suffering.