The Syrian government and rebels continue to disagree about the conference
The UN-Arab League envoy on Syria has said that a peace conference he hoped to hold in Geneva this month has been delayed, but he is still "striving" for a summit by the end of the year.
Lakhdar Brahimi said after a day of meetings with senior diplomats that he was not able to announce a date.
Attempts to set up a conference have been going on for months amid disputes over who should attend and its agenda.
Mr Brahimi said he would meet US and Russian diplomats again on 25 November.
"We were hoping that we'd be in a position to announce a date today, unfortunately we're not," he told reporters.
"But we're still hoping that we'll be able to have the conference before the end of the year."
The envoy added that "nothing dramatic" had happened at Tuesday's talks and the failure to agree a date had been expected for several weeks.
Mr Brahimi held talks with the US under-secretary of state and Russia's deputy foreign minister, then later with the other permanent members of the UN Security Council - the UK, France and China - as well as Syria's neighbours Lebanon, Iraq, Jordan and Turkey.
The idea of a conference was first mooted in May, and in September UN Secretary General Ban Ki-moon announced a tentative date of mid-November after the Security Council passed a binding resolution on Syrian chemical weapons.