US Secretary of State John Kerry will head to Moscow on Tuesday for talks with President Vladimir Putin on the Syrian crisis and the fight against Daesh, the State Department said.

"They will discuss ongoing efforts to achieve a political transition in Syria," spokesman Mark Toner said on Friday on the sidelines of the UN climate summit in Paris.

The talks will also cover differences in the parallel Russian and US approaches to the fight against Daesh in Iraq and Syria.

The US envoy will also bring up the ongoing stand-off in eastern Ukraine, where Moscow stands accused of supporting pro-Russian separatist rebels, Toner said.

Kerry will also meet his counterpart Foreign Minister Sergei Lavrov.

He arrives overnight from Paris for a day of high-level dialogue before flying back to Washington.

The United States and Russia are the key sponsors of the international bid to mediate an end to the Syrian civil war through the International Syrian Support Group.

This 17-nation contact group had been planning to meet in New York under United Nations auspices on December 18 to push forward plans for a negotiated ceasefire.

But Moscow and Washington were awaiting the results of a meeting between Syria's splintered opposition and rebel movements before confirming the date of meeting.

The rebels met on Thursday in Saudi Arabia and afterwards announced the composition of their team to open negotiations with the government of President Bashar Al Assad.

But they also insisted that Assad must step down immediately at the start of the political transition process, which has a January 1 target date.

This insistence may be a sticking point for Assad's allies in Moscow, and Kerry confirmed Friday he was working with the Saudis to iron out some "kinks" in the rebel plan.