On the eve of the talks, ten months after the last round of negotiations in the Swiss city, Russia called on Syrian President Bashar al-Assad to stop his bombing campaign during the discussions.
But just hours after rival delegations arrived, UN envoy Staffan de Mistura admitted there was limited ground for progress on making peace.
"Am I expecting a breakthrough? No, I am not expecting a breakthrough," the veteran diplomat said, noting that "momentum" toward further talks was likely the best that can be hoped for.
The government delegation is headed by Syria's UN ambassador Bashar al-Jaafari and the main opposition High Negotiations Committee (HNC) is led by cardiologist Nasr al-Hariri and lawyer Mohammad Sabra.
On the eve of the talks an HNC spokesman said the umbrella group wanted face-to-face discussions with government representatives."
We ask for direct negotiations... It would save time and be proof of seriousness instead of negotiating in (separate) rooms," Salem al-Meslet told AFP.
During three previous rounds of talks in Geneva last year, the two sides never sat down at the same table, instead leaving de Mistura to shuttle between them.
This time, de Mistura has voiced hope that he will manage to bring the two sides together for direct talks.
But when he was asked about the prospect during a press conference in Geneva on Wednesday, the UN envoy was cautious, saying he wanted to talk with the two sides bilaterally first.
The ground -- both in territory and diplomatically -- has shifted since the last UN-sponsored talks broke up in April 2016, and the rebels are in a significantly weaker position.
The army has recaptured the rebel bastion of eastern Aleppo and the United States, once staunchly opposed to Assad, has said it is reassessing every aspect of its Syria policy under President Donald Trump.
But the toughest issues remain similar to a year ago.
The latest truce was brokered in late December by opposition supporter Turkey and regime-backer Russia ahead of separate negotiations that also involved Iran in Kazakhstan.
The deal has reduced violence but fighting flared again this week including a government bombing campaign on rebel territory around Damascus.The HNC charged that Assad was trying to send "a bloody message" before the talks resume.
A bitter dispute over Assad's fate also continues to divide the camps. The HNC has insisted he must leave office as part of any deal, while Damascus has said the president's future is not open for negotiation.
De Mistura's office earlier said that the talks remain focused on "political transition". For the UN, that term can include a broad range of scenarios but the opposition sees it as implying Assad's removal.
Forcing the Syrian president from power had been the stated goal of Barack Obama's administration but Trump's election has muddied the US stance.
Trump has said that defeating the Islamic State group is Washington's top priority in the region and that the US would be narrowly focused on American interests.
The UN envoy acknowledged that the change of leadership in Washington had injected new uncertainties into the peace process.
"I'm not criticizing. I'm not complaining," he told reporters but added that all camps were looking "forward to seeing what their strategy is."
For the Syrian opposition there is urgency - this is the fourth round of UN-brokered talks, and violence which has killed more than 310,000 people over the last six years.
"We hope to see something achieved here in Geneva 4 because there is no way Syrians will be moving to Geneva 5 with this cost they are paying in Syria," said the HNC spokesman.
"We hope to end it right now here".