United Nations Special Envoy for Syria Staffan de Mistura has been meeting separately with Syrian government and opposition delegations this week during the latest round of talks, hoping to bridge gaps between the rival sides, while ensuring any outcome is consistent with previously adopted U.N. Security Council resolutions.
Dubbed as "proximity talks" in which government and opposition delegations are not expected to speak face to face, the latest gathering marks the third round in 2017.
This image provided by the State Department and DigitalGlobe, taken Jan. 15, 2015, a satellite image of what the State Department described as a building in a prison complex in Syria that was modified to support a crematorium.
The U.S. State Department said on Monday that as many as 50 prisoners a day are being killed at the Saydnaya prison, one of Syria's largest and most secure prison complexes. It alleged that the government of President Bashar al-Assad then uses a crematorium installed inside the Saydnaya facility to hide evidence of the mass killings.
Syria's Foreign Ministry denied the U.S. allegation, calling it a "Hollywood story detached from reality."
Syria's opposition has been pressing the detainee issue for some time but met with limited progress. Advocacy group Human Rights Watch said its research found the systematic and widespread treatment of detained civilians in prisons across Syria, including Saydnaya prison, amounts to crimes against humanity.
"The parties should agree on ensuring access by independent monitors to Syrian government detention centers and prisons," said Sarah Margon, Human Rights Watch's Washington director.
"Ultimately, accountability for the treatment of detainees will need to be part of a comprehensive U.S. policy for Syria," Margon added.
In this photo released by the Syrian official news agency SANA, Syrian President Bashar Assad, right, meets with Iraq';s National Security Adviser Faleh al-Fayadth, in Damascus, Syria, May. 18, 2017.
Important step for US
The rights group also said Washington's recent push on Moscow over the Syrian government's treatment of prisoners is an important step to bring more pressure to bear on Bashar al-Assad's daily atrocities.
"The detainee file must be at the forefront of talks in Geneva," according to "Save Our Syria," a coalition of Syrian civil society and humanitarian groups, adding, 'In order for the Syrian political process to be credible, it must deliver concrete progress on the detainee file - a chief concern for the hundreds of thousands of Syrian families that have been affected by Assad's mass detention."
Past Geneva talks have produced the agreement that the warring sides will discuss agendas including a new constitution, reformed governance, new elections and the fight against terrorism, but progress has not yet been made.
'Slim at best'
Some analysts said the chances of progress at the new talks at Geneva are "slim at best."
"Detainee issues will be a priority for the U.S. and for the U.N., but the Syrian government will simply deny everything. Progress on the issue is unlikely," Daniel Serwer, professor of conflict management at the Johns Hopkins School of Advanced International Studies told VOA.
This week's talks follow a deal by Russia, Turkey and Iran to arrange and monitor the so-called "de-escalation zones" in Syria to reduce the violent conflicts.
"These new accusations from the State Department appear to be an attempt to pressure Russia even more strongly into exerting influence on Assad to play by the rules of law," Middle East Institute Senior Fellow Charles Lister told VOA.
'For now, the international community's energy would be better focused on talks aimed at de-escalating the conflict on the ground in order to generate conditions more amenable to a meaningful political process,' he added.
In Geneva, a spokesperson from the High Negotiations Committee, the main Syrian opposition group, said on Wednesday, 'We're here to try to save lives; but, the other party does not care about the lives of Syrians.'
Russia and the United States both regard the Islamic State militant group as an enemy and share limited information about terrorist threats. But the two nations have competing agendas in Syria, where Moscow has deployed military assets and personnel to support Assad.
The top U.S. diplomat for the Middle East, Acting Assistant Secretary Stuart Jones, urged Russia to "exercise its influence over the Syrian regime to guarantee that horrific violations stop now" with great urgency.