Senior diplomats from the West and the Middle East are to meet once again in Vienna in an effort to salvage stumbling efforts to halt Syria's bloody civil war, Al Jazeera reported.
United States Secretary of State John Kerry and Russia's Foreign Minister Sergey Lavrov, at loggerheads over much else in the world, will chair the meeting on Tuesday.
At the gathering, the 17-nation International Syria Support Group (ISSG) will renew its call for a national cessation of hostilities and immediate humanitarian access to besieged communities.
But the third plank of the plan - a call for Syrian President Bashar al-Assad's regime and the rebels to agree on a "framework for political transition" - may cause headaches.
US officials travelling with Kerry say Washington still insists that Assad should go, with an August 1 deadline for settling on the framework under which he does so.
But the Syrian president, bolstered by military support from Russia and Iran, has shown no sign he is prepared to leave and his forces are still battling for territory.
"There's a sentiment here in Vienna that it may take some time to bridge the gap between the two key players," said Al Jazeera's Hashem Ahelbarra, reporting from the Austrian capital.
"We've been talking to members of the Syrian opposition, They say they have lost trust. If they don't get clarity about Assad, they won't sign anything."
United Nations-brokered peace talks in Geneva ended last month without any progress after the delegation of the opposition walked out, citing surging attacks by regime forces and its Russian ally, as well as problems with humanitarian aid shipments.
In the past weeks, more than 300 people have been killed in regime air strikes in Aleppo province alone, while deadly fighting has also raged in other parts of Syria, including Idlib, Deir Az Zor and outskirts of Damascus.
A truce deal in place since February does not cover the armed groups such as Islamic State (IS) and al-Nusra Front, al-Qaeda's Syria branch.
While the Syrian opposition demands that the president step down and pave the way for a political transition, the government delegation in Geneva has so far refused to talk about such a scenario.
Iranian Foreign Minister Mohammad Javad Zarif said his country supported the truce and a peace dialogue, but he warned that a silencing of arms might aid armed groups operating in Syria.
"We should not allow terrorists to use the cessation of hostilities for further terror operations," he said.
Moscow, Assad's key foreign backer, supports the ISSG platform on paper but backs Syrian government forces on the ground.
Russia nevertheless endorsed the UN Security Council resolution that enshrined the ISSG peace plan in international law - and Lavrov says he supports it.
The talks come as fighter jets from the US-led coalition continue their attack on IS targets in Aleppo, while Western-backed rebels have launched their own offensive on the ground.
Meanwhile, a regime air strike in the city left at least three civilians dead early on Tuesday, among them a mother and her young daughter, according to the Syrian Observatory for Human Rights.
Regime forces continue to blockade several rebel-held areas around Damascus, stopping all food and medical aid in defiance of UN Security Council resolutions.
And IS and the al-Nusra Front, not party to the ceasefire or peace talks, still hold vast swaths of the country and carry out attacks.
In Bdama in Idlib province in the northwest, large swaths of which are held by Al-Nusra, regime strikes left eight civilians dead, including four women and three children.
Fighting has also broken out between al-Nusra Front and other factions, killing more than 300 fighters in recent weeks.