Some armed Syrian opposition groups have decided to attend peace talks with the government next week in Kazakhstan's capital, Astana, according to rebel officials.
The discussions, scheduled for January 23, intend to build on a nationwide ceasefire that has largely held despite escalating violence across several battlefronts in recent days.
Mohammad Alloush, a leading figure in the Jaish al-Islam group, said on Monday he would head the rebel delegation to the meeting.
He said the rebels were going to the talks to "neutralise the criminal role" of Iran in Syria's conflict.
"All the rebel groups are going [to Astana]. Everyone has agreed," Alloush told AFP news agency.
"Astana is a process to end the bloodletting by the regime and its allies. We want to end this series of crimes."
The rebel factions' decision to send a delegation to the Astana talks came after five days of negotiations in Turkey's capital, Ankara.
The High Negotiations Committee, Syria's main opposition bloc, had also said previously that it would extend its support to an anti-government military delegation attending the talks.
But Shaam Network, an opposition news website, reported on Monday that a number of other rebel groups, including Ahrar al-Sham, one of the main fighting forces on the ground, had decided to stay away from the upcoming talks.
"At this point in time, six years into this war, the different brigades still cannot speak with one voice when it comes to Syria," Al Jazeera's Stefanie Dekker, reporting from the Nizip refugee camp in Turkey, said.
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President Bashar al-Assad of Syria has already said his government is ready to attend the Astana meeting and "discuss everything".
The participating factions said on Monday the talks will only focus on reinforcing the current truce and look at humanitarian issues; a possible political solution to the crisis will not be on the agenda.
Zakaria Malahifji, of the Fastaqim rebel group, said: "The majority of the groups decided to attend. Discussions will be on the ceasefire [and] the humanitarian issues - aid deliveries, release of detainees."
The Astana meeting is organised by Russia and Turkey - two countries that have backed opposing sides of Syria's conflict for years, but have worked closely in recent weeks to end the bloodshed.
An official in a Free Syrian Army rebel group that agreed to participate in the talks told Reuters news agency on Monday the meeting would "be a test for the Russians as the guarantor".
He declined to be identified because the rebel groups had yet to appoint a spokesman.
If the Astana meetings are successful, they could bode well for the fate of fresh UN-hosted negotiations on the conflict next month in Switzerland's Geneva.
Several rounds of peace talks held by the UN have failed to produce a political solution to the conflict.
"We know the Astana talks are not going to be easy," said Al Jazeera's Dekker.
"Many of these groups did not want to attend them at all - certainly the political opposition, which has always said ... the talks need to be seen as a stepping stone for the UN-sponsored talks in Geneva."
The truce, which began in Syria on December 30, to pave the way for the new peace talks, excludes the Islamic State of Iraq and the Levant (ISIL) group and Jabhat Fateh al-Sham, which changed its name from al-Nusra Front after breaking ties with al-Qaeda last year.
Russia, Assad's most powerful ally, set the new diplomatic effort in motion after Syrian rebels suffered a major defeat last month by losing the rebel-held districts of eastern Aleppo.
Mevlut Cavusoglu, Turkey's foreign minister, said on Saturday that Turkey and Russia had decided to invite the US to attend the Astana meeting.
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However, a Kremlin spokesman did not confirm that on Monday.
As with last year's peace talks, powerful Kurdish groups that control wide areas of northern Syria are being excluded from the talks in line with the wishes of Turkey.
Syria has been engulfed by violence since widespread protests in March 2011 calling for Assad's removal.
More than 310,000 people have been killed and over half the population has been forced to flee.
Source: Al Jazeera and news agencies