UN chief Ban Ki-moon is convinced that Geneva peace talks are the best way to resolve the Syrian conflict and urges all sides to return to the table, his spokesman said.
The UN Security Council meanwhile met Tuesday to discuss a resolution on the humanitarian situation in Syria, but Western nations and Russia disagree on several points.
Jordan's UN ambassador, Prince Zeid al-Hussein, said he hoped for a vote by the end of the week.
Diplomats said the talks in the council had stumbled over the possibility of sanctions against any party that blocks delivery of humanitarian aid to desperate civilians caught up in the war.
Russia, Syria's main ally, opposes any threat of sanctions but Western nations say any new resolution must contain binding language to this effect to have any weight.
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Since the war broke out in March 2011 Russia has blocked three resolutions that aimed to increase pressure on President Bashar al-Assad.
Just weeks after the warring parties sat down for the first time to seek a political settlement to the three-year civil war, a second round ended in acrimony over the weekend.
"The secretary general remains convinced that Geneva II is the way to go, and he is looking at the parties to think long and hard and to come back as soon as possible so that this process can continue," spokesman Martin Nesirky told reporters.
"This is a process, not a single event taking place in one or two meetings... this is going to take a long time."
"The secretary general remains determined to push ahead with this, as is (UN mediator Lakhdar) Brahimi," Nesirky added.
Brahimi said Saturday he was "very, very sorry" after the talks between the Syrian regime and the opposition broke off without result after three weeks. No date has been set for a resumption of negotiations.
Nesirky said Brahimi would be coming to New York "at some point" to brief Ban and the Security Council on his mission.