U.S. Hopes to Hold NY Syria Talks Next Week, Russia Says 'Premature'

World powers are still working out details of the next talks on ending the war in Syria but hope to hold them next week, U.S. Secretary of State John Kerry said Tuesday.

Earlier, the Russian foreign ministry had said it was too early to confirm that the next round of negotiations would go ahead in New York on December 18.

Russia and the United States are the main sponsors of the talks, which aim to mediate a ceasefire and political talks between President Bashar Assad's regime and opposition rebels.

Speaking in Paris alongside U.N. Secretary General Ban Ki-moon, Kerry admitted that details of the rebel representation in the process are still being ironed out. 

"Depending on the outcome of both the Saudi-led conference of the opposition that is taking place in the next days, as well as a few other issues, it is our plan to try to attend and have a meeting in New York on December 18," he said.

"But again, it depends on the flow of events over the next week. That is our current plan and we hope to be able to do that."

Saudi Arabia has taken the lead in drawing together a wide array of groups opposed to both Assad and the Islamic State jihadist group, hoping to produce a unified opposition for hoped-for negotiations with the Syrian leader.

But earlier, Russia -- a key ally of Assad -- said that in the absence of progress on this front it would be "premature" to announce a date for talks. 

"Not having a collective understanding of who in Syria is a terrorist and who is an opposition member, it is impossible to hold talks on the internal Syrian political process or on such an important and urgent matter as the ceasefire," the foreign ministry said in a statement. 

"We don't need to hold a meeting just for the sake of meeting."