Representatives from Russia, Turkey and Iran have kicked off a technical meeting in Kazakhstan's capital Astana to discuss details of the implementation of the Syrian ceasefire agreement.
The meeting comes two weeks after the three countries reached an agreement in Astana to create a trilateral mechanism aimed at monitoring breaches of a fragile truce established in late December and paving the way towards UN-led peace talks in February.
Representatives of Jordan are also expected to take part in Monday's meeting.
The agenda for the meeting, according to a spokesperson for Kazakhstan's foreign ministry, includes a review of the ceasefire implementation, and a discussion of a proposal submitted from the Syrian armed opposition about the truce.
"This is about creating a mechanism to control the implementation of the ceasefire," the ministry spokesman said.
The parties also plan to discuss cooperation on humanitarian issues and increasing levels of trust between the Syrian government and the opposition.
The Kazakh foreign ministry gave no information about the line-up of the delegations, who were meeting behind closed doors.
Talks last month in Astana brought together representatives of the Syrian government and armed opposition groups for the first time since the beginning of the Syrian war in 2011.
The two-day Astana talks, organised by Russia and Turkey, came as Moscow takes the diplomatic lead in the war after its 2015 military intervention helped turn the tides of the conflict in favour of Syrian President Bashar al-Assad.
Before the meetings began, observers expected to see the first face-to-face negotiations between the government and representatives of the armed opposition since the war began, but rebels refused to participate in direct talks over ceasefire violations.
The Russian delegation spent the two days shuttling between meetings with the Syrian government, the Iranian delegation - one of the Syrian government's strongest allies, the opposition, and Turkey - a key backer of rebel groups operating in the country.
The talks marked the beginning of the latest diplomatic initiative to put an end to nearly six years of war which have left much of the country in ruins, killed nearly half a million people, and displaced half of the population.
Russian Foreign Minister Sergey Lavrov said on Sunday the Astana talks were a "breakthrough step" in efforts to resolve the crisis but were not intended to be a substitute for UN-led talks.
"We are not planning to replace Geneva with the Astana format," he said in an interview published on the ministry's website.
The talks spotlighted sharp differences between Moscow and Tehran over the possible future participation of the United States and also excluded Gulf states, both major backers of armed opposition groups in Syria.
Iran, whose relations with Washington have nosedived since Donald Trump assumed the presidency, opposes any US involvement.
Lavrov reiterated on Sunday that the US and Moscow were in a position to solve bilateral issues, improve ties and coordinate efforts to fight "international terrorism", but said it had to be on the basis of mutual respect.
The secretary of Iran's Supreme National Security Council, Ali Shamkhani, also praised the Astana talks in a meeting with Russia's special envoy on Syria, Alexander Lavrentiev, in Tehran on Sunday, according to the Islamic Republic News Agency (IRNA).
But he said peace was not achievable with certain groups still active on the ground - specifically the Islamic State in Iraq and the Levant (ISIL), and Jabhat Fateh al-Sham, known as al-Nusra Front before officially cutting ties with al-Qaeda.
"As long as Daesh [ISIL] and al-Nusra and groups linked to them are present in Syria - and they are being protected and supported by some countries in the region - a political solution and peace for Syria and the region will not be achievable."
The Syrian opposition have objected to Iran's role in the Astana talks, blaming Shia militias backed by Tehran for violations of the fragile ceasefire agreement by launching military assaults in rebel-held suburbs of the capital.
UN special envoy Staffan de Mistura said the UN would attend a follow-up technical meeting in Astana on February 6 to further discuss the implementation and monitoring of the ceasefire.