UN-brokered talks aimed at setting up a conference to end the war in Syria have finished without agreement.

US and Russian officials failed to agree on many questions, including the dates and participants, Russian Deputy Foreign Minister Gennady Gatilov said.

The two sides will return to their capitals to discuss how to take the process forward.

However, there was still no agreement on who would represent the Syrian opposition and whether Iran would be at the table, he told reporters after the five-hour talks.

US Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov will meet next week, and further talks on the conference were expected to follow, a UN statement said.