Geneva - UN mediator Lakhdar Brahimi met Syria's warring sides behind closed doors on Thursday to lay the groundwork for direct talks after the first day of a peace conference ended in bitter exchanges.
Brahimi met separately with delegations from Syria's opposition and then President Bashar Assad's governemnt in Geneva before full talks are due to resume on Friday.
It was unclear after the meetings whether the two sides would agree to hold face-to-face talks or if mediators would shuttle between them.
A senior US State Department official said Brahimi was due to meet with both sides again on Friday morning with the goal of having them in the same room by the afternoon.
"He hopes to have them at the table tomorrow and we'll see what happens," the official said. "We knew this would not be an easy process."
"We know this is going to take some time, and if it takes an extra day, it takes an extra day," the official added.
The UN-sponsored conference - the biggest diplomatic effort yet to resolve Syria's devastating civil war - opened in the Swiss town of Montreux on Wednesday with heated disagreements among the two sides and world powers.
Expectations are low for a breakthrough at the conference, which officials have said could last up to 10 days, but diplomats believe that simply bringing the two sides together for the first time is a mark of some progress and could be an important first step.
"We've begun the process, getting the parties in the same room is significant, having them in Geneva is significant," the US official said.
With no one appearing ready for serious concessions, mediators will be looking for short-term deals to keep the process moving forward. They could include localised ceasefires, freer humanitarian aid access or prisoner exchanges.
Brahimi said he "had indications" from both sides that they were willing to discuss these issues.
Syrian state media slammed the Montreux conference, with the Tishreen daily charging that most of the speeches from the more than 40 nations and international bodies present had lobbed "dishonest accusations... at the Syrian government".
"The imposters were unmasked. They spoke out in favour of terrorism while making speeches about justice and human rights," the Al-Thawra daily said.
The opposition arrived in Switzerland with a sole aim - toppling Assad - while the government says any talk of removing the Syrian leader is a "red line" it will not cross.
Hadi Al-Bahra, a member of the opposition National Coalition's delegation, told AFP the opposition felt it had benefited from the government’s aggressive tone at the start of the conference Wednesday.
"We have heard very positive feedback from inside Syria and it is the first time we've felt so much support from Syrians for the Coalition," Bahra said.
During his opening speech, Foreign Minister Walid Muallem accused the opposition of being "traitors" and agents of foreign governments.
UN leader Ban Ki-moon urged the two sides at the conference to finally work together to save lives.
"The world wants an urgent end to the conflict," Ban said in his closing press conference. "Enough is enough, the time has to come to negotiate."
Notably absent from the Montreux conference was crucial Assad backer Iran, after Ban reversed a last-minute invitation when the opposition said it would boycott if Tehran took part.
In the Swiss ski resort of Davos on Thursday, Iranian President Hassan Rouhani said elections would be the best way to end Syria's civil war.
"The best solution is to organise free and fair elections inside Syria," Rouhani told the World Economic Forum. "No outside party or power should decide for the Syrian people and Syria as a country."
Erupting after the government cracked down on protests inspired by the Arab Spring, Syria's civil war has claimed more than 130 000 lives and forced millions from the homes.
Pitting Assad's government, dominated by the Alawite offshoot of Shi’ite Islam, against largely Sunni Muslim rebels, the war has unsettled large parts of the Middle East.
Shi’ite Iran and its Lebanese militia ally Hezbollah have backed Assad. The mainly Sunni Arab Gulf states have supported the opposition. And the violence has often spilled over into neighbouring Lebanon and Iraq.
Sectarian clashes linked to Syria's war have killed 10 people in Lebanon's northern city of Tripoli over the past six days alone, a security official said on Thursday.
Much of the fighting inside Syria in recent weeks has been between opposition forces themselves, as rebel groups combined to attack bases of the Islamic State of Iraq and the Levant, or Isil, an al-Qaeda linked group.