Kerry met Putin on Thursday evening with a proposal to boost military and intelligence cooperation against "Islamic State" (IS) and al-Qaeda's affiliates in Syria.

In exchange, Washington hopes it can make Russia persuade Syrian President Bashar al-Assad to ground his planes and halt attacks on civilians and moderate opposition groups.

The three-hour meeting broke up at 1 a.m. local time, and the two gave little away. However, US State Department spokesman John Kirby said Kerry had expressed concern about repeated violations of the cessation of hostilities by the Syrian regime.

"The two also discussed the need to need to increase pressure on terrorist groups like Daesh and the al-Qaeda affiliate in Syria, Jabhat al Nusra," said Kirby.

Earlier, Putin said a telephone call with US President Barack Obama had led him to believe Moscow and Washington shared common interests.

"My last conversation with President Obama has convinced me that we are indeed striving not only to establish a process of cooperation but also to achieve important results."

Sitting across from him, Kerry agreed Obama had found the recent telephone call "constructive." The Secretary of State said he and Obama believed that Russia and the US were in a position to make "an enormous difference" when it came to both Syria and Ukraine.

On Friday, Kerry was scheduled to hold more detailed talks with his Russian counterpart Sergey Lavrov.

Joint base in Jordan?

Citing a draft proposal by the US, The Washington Post reported that the US and Russia could set up a joint command and control center in Jordan, which would direct intensified air strikes against al-Nusra. The jihadi group is mainly fighting Assad's forces, and Washington appeared to play down the significance of any military offer.

The US and Russia, and the 22-nation contact group they co-chair, have urged a nationwide ceasefire and Geneva-based talks on a "political transition."

A landmark partial ceasefire was brokered in February, but it did not include IS or Al-Nusra. That fragile peace has since all but collapsed.

UN Syria envoy Staffan de Mistura urged Moscow and Washington to press for talks to resume next month. De Mistura said the talks "have a target date of August" and would have to be "a credible beginning of a roadmap towards a political transition."

rc/bw (AFP, Reuters)