Russian Federation is struggling to salvage its bid to secure a deal to end six years of civil war in Syria as deepening differences with Iran risk a repeat of previous failed peace efforts led by the U.S.
"Russia is in a very hard position, it's being torn between its traditional partners, Assad and Iran, and its potential partners in the fight against Islamic State - Turkey and the USA", said Alexander Shumilin, head of the Middle East Conflicts Center at the Institute for US and Canada Studies, a government-run research group in Moscow.
United Nations envoy Staffan de Mistura has invited opposition groups and representatives of the Syrian government to Switzerland in a fresh diplomatic bid to move toward a political solution to the six-year-old conflict in Syria.
During negotiations with Syrian government's representatives in Geneva, opposition member Colonel Fateh Hassoun said that the delegation is in possession of "visual evidence" that confirms the government's involvement with ISIS.
"We met with (Syrian government negotiator Bashar) Ja'afari and he reconfirmed that he is not against the agenda proposal, but he said that terrorism should not be ignored and should also be on the agenda", Gatilov said.
Russia's delegation looks set to meet the High Negotiations Committee (HNC), the main opposition group, in Geneva on Wednesday, with the Assad opponents urging Moscow to step up pressure on Damascus.
"Definitely yes", deputy foreign minister Gennady Gatilov told reporters when asked if terrorism should be included. The Syrian leader, confident after military advances with the help of Russian air power that led to the capture of the former commercial capital Aleppo in December, maintains the fight against terrorism is the priority.
Unconditional 'Geneva 4' Talks on Syria
The Al-Nusra Front terror group, which renamed itself into itself Jabhat Fateh al-Sham, has claimed responsibility for the attack.
The Assad government's delegation chief, Bashar al-Jaafari, demanded at the weekend that all opposition factions present in Geneva condemn a suicide assault that killed dozens Saturday near Syria's third city of Homs.
The Syrian opposition at Geneva IV peace talks said Wednesday they had been told by United Nations mediator Staffan de Mistura that the regime delegation had agreed to discuss the issue of political transition.
"I think it's about time for Russians to understand that if they keep avoiding working with HNC, in a few years it might happen they will be sitting in front of ISIS leaders and trying to find solutions for Syria", Atassi said, using an acronym to refer to the Islamic State in Iraq and the Levant (ISIL, also known as ISIS).
Gatilov was cautious in his assessment of hopes for the latest Geneva talks.
Reuters reported the diplomats as saying the resolution would likely be vetoed by Russian Federation, as it has previously announced, but "with Geneva on at the same time, we think this resolution sends a strong message".
Nasr al-Hariri says the meeting will "most likely" take place on Tuesday.
A ceasefire backed by Russia, Iran and Turkey has not stopped the fighting.