Syria should hold elections within 18 months, groups opposing the Syrian president should be involved in future talks about the country's political process, and a truce - minus two rebel groups - should be put in place immediately, according to world leaders.
The leaders met in the Austrian capital Vienna on Saturday to chart a way towards a ceasefire and political transition to end the country's war.
Following the talks, US Secretary of State John Kerry said negotiations between the Syrian government and opposition should start by January 1.
Kerry added that the Islamic State of Iraq and the Levant (ISIL) group and al-Nusra Front were designated as terrorist organisations and would not be part of a ceasefire or talks.
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Addressing reporters alongside the Russian Foreign Minister Sergey Lavrov and UN Special Envoy for Syria Staffan de Mistura, the US official said that a transitional government for Syria is to be set in six months, with hopes for elections in 18 months' time.
He added, however that, "we still differ on what happens to [Syrian President] Bashar al-Assad".
Lavrov said that the majority of delegates wanted an immediate ceasefire in Syria.
Al Jazeera's Mohammed Jamjoom, reporting from the Austrian capital, said: "This seems to be a pretty big breakthrough."
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Previous rounds of talks held in Vienna in recent weeks, also with delegates from several countries including those vested in Syria's war - Iran, Saudi Arabia, Russia, the US, and Turkey - had failed.
"They are committed to getting this done under the auspices of the UN," our correspondent added. "But regarding the inclusion of the opposition - that's going to be tricky. The opposition is a fractious body, there are a lot of different groups that claim to be the legitimate Syrian opposition.
"The call for elections within 18 months is also a tall order."
Evan Barrett, an adviser to the US-based Coalition for a Democratic Syria, said Russia seeks to persuade Western states to reclassify some Syrian rebel groups as terrorists in a bid to bolster Assad's government.
"Without any guarantees over the fate of Assad, the prosecution of war crimes, or opposition participation in a future government, it's hard to see how the opposition could accept this framework," Barrett told Al Jazeera.
The meeting came under extra pressure as the aftermath of a deadly round of attacks in France's capital took centre stage.
"Daesh [ISIL] has claimed it is behind this," said Kerry. "We have seen nothing to lead us to a different conclusion," he said in French after the talks.
Kerry earlier said that the attacks were an "assault on our common humanity", and promised that the violence had strengthened the group's resolve to find solutions to end Syria's war.
In Syria, Assad's forces, emboldened by Russian and Iranian support, this week seized an opposition bastion on the Aleppo-Damascus highway and broke a siege by ISIL on Kweires airbase in the east of Aleppo province.
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According to Jennifer Cafarella from the Institute for the Study of War think-tank, pro-government forces are enjoying a "morale boost" and appear poised to retake the besieged Shia villages of Kafraya and Fuaa and advance on Idlib province.
The UK-based Syrian Observatory for Human Rights says that Russian air strikes from September 30 until October 31 killed at least 185 civilians, including 46 women and 48 children.
During the same period, Russian air strikes also killed at least 279 fighters, the monitor added.
More than 250,000 people have been killed in the Syrian war. Eleven million have been uprooted from their homes.
Europe and Syria's neighbours, meanwhile, are struggling to cope with the influx of refugees trying to escape war.
Al Jazeera's Jamjoom said that refugees from Syria and Iraq, whom he had spent time with over the past two weeks in Greece, were concerned that attacks in Europe would further harm their plight.
"They are the ones left out in the cold right now," he said.
With reporting from James Reinl: @jamesreinl
Source: Al Jazeera and agencies