The UN-Arab League envoy to Syria has met senior diplomats in the Swiss city of Geneva in a new push to prepare a long-delayed peace conference.
Lakhdar Brahimi's meetings on Tuesday came as Russia insisted that Iran must be invited to the peace negotiations.
"All those who affect the situation must be invited to the conference," Sergey Lavrov, Russian foreign minister, said.
"This includes all of Syria's neighbours, this includes almost all countries of the Persian Gulf including, of course, not only the Arab countries but also Iran, this includes the permanent members of the UN Security Council, and other countries such as Turkey."
Brahimi began talks with Gennady Gatilov and Mikhail Bogdanov, Russian deputy foreign ministers, and Wendy Sherman, US under secretary of state for political affairs, on Tuesday morning at the UN's European headquarters.
Representatives of the three other permanent members of the UN Security Council, China, France and Britain, will join the meeting later on Tuesday.
Al Jazeera's Simon McGregor-Wood, reporting from Geneva, said, "There seems to be no shortage of understanding in the international community and in the Middle East region itself that a peaceful solution is the only solution."
"Part of the problem is that everyone in the region and internationally claims a role in solving the issue, and they all claim a strategic interest in what Syria will eventually look like," he said. "Some might call that 'meddling'."
A UN announcement that Syria's neighbours, Iraq, Jordan, Lebanon and Turkey, as well as the UN and the Arab League would take part in Tuesday's talks was seen as an indication preparations for the conference, dubbed Geneva II, were finally picking up speed.
But it remains unclear whether the parties will manage to agree on who should participate and whether they can find a way to end the 31-month conflict that has killed more than 120,000 people and forced millions more to flee their homes.
Reject rebel participation
Syria's opposition has refused to attend peace talks unless President Bashar al-Assad's resignation is put up for discussion, a demand rejected by Syria.
Ahmad Jarba, Syrian opposition leader, has also rejected the rebels' participation if Iran is asked to attend.
Jarba, who heads the main umbrella opposition National Coalition, emphasised the group's commitment to attending Geneva II only as a united front and reiterated its unequivocal demand for a ceasefire during the talks.
The coalition has said it plans to meet in Istanbul, Turkey, on Saturday to decide whether to attend the peace talks, but the Syrian National Council, a key member of the bloc, has threatened to quit if it does so.
Brahimi has said that "if the opposition does not participate there will be no Geneva conference".
The veteran Algerian diplomat said after a meeting with Assad in Damascus last week that the Syrian government had agreed to take part in the talks while the opposition was "trying to find a way to be represented".
"We hope it will take place in the next few weeks, not next year," he said.
The conference is meant to follow up on a meeting last year that produced a transition plan for the war-ravaged country which was never implemented.
Late on Monday, Syria's information minister said that the regime would not take part in the proposed conference if the aim is for Assad to give up power.
"We will not go to Geneva to hand over power as desired by [Saudi Foreign Minister Prince Saud] al-Faisal and certain opponents abroad," Omran al-Zohbi said in comments carried by the official SANA news agency.