Under pressure from global backers, the two sides have agreed to discuss a new constitution, reformed governance, new elections and the fight against terrorism, but they differ sharply over what those agenda items mean.
According to Meslet, HNC members discussed two main topics during their first meeting with United Nations special envoy Staffan de Mistura on Tuesday afternoon: a constitution for Syria, and thousands of prisoners in regime jails.
"The alternative is no discussion, no hope, no political horizon, just waiting for facts on the ground to take place", de Mistura told reporters. They do have an impact on what we discuss.
A senior Israeli official has called for President Bashar Assad to be assassinated over alleged atrocities in the Syrian civil war.
Mr Assad has said "nothing substantial" will come out of the talks.
He said "when we finish with the tail of the snake we can reach the head of the snake sitting in Tehran and deal with it as well". Syria denied the allegations.
According to a report by the Syrian Center for Policy Research, the conflict has claimed the lives of over 470,000 people, injured 1.9 million others, and displaced almost half of the country's pre-war population of about 23 million within or beyond its borders.
De Mistura also met with deputy Russian foreign minister Gennady Gatilov earlier in the day, Moscow's foreign ministry said. Observatory director Rami Abdurrahman says IS fighters were also killed.
Accusations of the coalition's responsibility comes from local activists, who claim that forces approached eastward from Iraq, reported the Financial Times. Wael Abou Rayan, a media activist in the Homs countryside, says the bombardment of Homs eased since the agreement came into force, but never completely halted.
Syria nd is non-stopping armed conflict is in the centre of the United Nations' attention.
Tuesday's start of talks in Geneva were overshadowed by USA accusations that the government in Damascus carried out mass killings at a prison near the Syrian capital and then burned the victims' bodies in a crematorium.
De Mistura hoped all the delegations would desist from set piece press conferences, which he clearly feels lead to delegations making inflexible statements that impede private reconciliation.
A Syrian monitoring group says twin explosions have gone off in a makeshift camp near Syria's the border with Jordan, killing at least 10 people and wounding seven, including rebel fighters.
Assad, meanwhile, has brushed off the Geneva negotiations as "merely a meeting for the media".
The meetings were the sixth round of talks brokered by de Mistura.
The opposition position has weakened since the last round ended on March 31 after the government secured the evacuation of three rebel-held districts, bringing it closer to exerting full control over the capital for the first time since 2012.
The Syrian government on Tuesday "categorically" denied US accusations of mass killings at a prison near Damascus, including the alleged execution of political opponents and burning the victims in a crematorium at the site.