United Nations mediator Staffan de Mistura says that before negotiations are paused on Thursday he wants the Syrian regime to set down on paper its vision of a new government for leading the country out of five years of brutal conflict.
De Mistura has praised the main opposition High Negotiations Committee for submitting "substantive" ideas on political transition, but noted that through several meetings last week the government side's focus was limited to procedural issues and broad principles.
The UN envoy met with the government on Monday, before talks with the HNC on Tuesday.
The opposition contingent in Geneva has expanded with the arrival of HNC leader Riad Hijab, a former prime minister under President Bashar al-Assad who defected from his post in 2012.
Assad's fate is the toughest issue facing the talks. The HNC has insisted the president's departure be part of any peace deal, with the regime describing such demands as "a red line."
Through the weekend, when no formal meetings were held in Geneva, the regime blasted de Mistura for taking sides, while claiming negotiations had achieved nothing since resuming on March 14th.
HNC member Yahya Kodmani on Sunday charged the government with being "obstinate" and "refusing any serious discussion" about the central question of Assad's future.
A Western diplomat, who requested anonymity, told AFP that so far the regime has "not ... injected genuine thoughts into these negotiations".
In contrast, the HNC "is very constructively engaged" and worked through the weekend to prepare responses to de Mistura's questions about the opposition's political transition plan, the diplomat said.
The diplomat added that while a possible deal on a political transition remains a distant prospect, the two sides could move towards "a common understanding" by Thursday on broad principles and less contentious issues like the territorial borders of a post-conflict Syria.
De Mistura has acknowledged that huge divides remain between the camps but claimed the talks had already produced positive outcomes by helping maintain a fragile ceasefire declared on February 27th.
Assad ally Russia on Monday accused the United States of stalling on the enforcement of the truce and not committing to mechanisms for responding to violations.
Washington supports the HNC and some opposition forces fighting on the ground in the conflict that has killed more than 270,000 people and displaced millions.
In a statement, Russian lieutenant general Sergei Rudskoy said that, given the US feet-dragging, Moscow was ready to resort unilaterally to force against ceasefire violators as of Tuesday.
The truce has broadly held since being declared last month and allowed life-saving aid to reach tens of thousands of Syrians stranded in besieged areas.
The ceasefire does not include the Islamic State group (IS) and Al-Qaeda linked Al-Nusra Front, who continue to be targeted in Russian air strikes and government offensives.
At least 26 pro-government fighters were killed battling Islamic State near Palmyra on Monday as Damascus stepped up a bid to recapture the ancient city,the Syrian Observatory for Human Rights said.
Russia to pressure Assad?
Negotiations were rattled last week by Russia's surprise decision to withdraw most of its troops from Syria, a move that diplomats and experts said could help the peace drive by weakening Assad's position and forcing him to negotiate.
De Mistura has called the Russian pull-out a "positive" development and said if the talks stall he will turn to "those who have influence" to help clear the roadblocks, listing Moscow for its presumed ability to sway Assad.
The HNC's Kodmani on Sunday restated the opposition's belief that Moscow has the power to force the regime's hand.
"We hope that Russia will use its powers to pressure the Assad regime in order to move into serious negotiations on the political transition," he said.