The deal came despite initial pessimism from participants Thirty Syrian civilians attending a funeral were killed by mortar fire on Saturday, in the town of Zamalka, 10km (six miles) east of the Syrian capital of Damascus, the Syrian Observatory for Human rights said.
That brought to 82 the number of people killed in violence across the country, most of them civilians.
On the diplomatic front, world powers agreed a plan for a transition in Syria that could include current regime members, but the West did not see any role for President Bashar al-Assad in a new unity government.
Russia and China insisted that Syrians must decide how the transition should be carried out rather than allow others to dictate their fate, as the two powers signed up to the final agreement that did not make any explicit call for Assad to cede power.
The deal came despite initial pessimism from participants about the prospects of the Geneva talks amid deep divisions between the West and China and Russia on how to end the violence.
Rights monitors said most victims were civilians and hundreds more were trapped in Douma as regime forces stormed the town in Damascus province.
While international envoy Kofi Annan did not name names and said it was up to the Syrians to decide who they wanted in a unity government, he added: \"I would doubt that Syrians... would select people with blood on their hands to lead them.\"
US Secretary of State Hillary Clinton made it clear that Washington did not see a role for Assad in the transition.
\"Assad will still have to go. He will never pass the mutual consent test,\" she said.
French Foreign Minister Laurent Fabius took the same stance, saying, \"It\'s clear that Assad must stand down\".
\"No one can imagine for a moment that Assad will feature in the (new) government, any more than anyone thinks it possible for him to establish a neutral environment\" required by the agreement, he said, adding that the transition government \"will exclude murderers.\"
British Foreign Minister William Hague admitted that the deal was a \"compromise agreement\" as Russia played up the fact that it had convinced other world powers that it would be \"unacceptable\" to exclude any party from the transition process.
A long-time Syria ally, Russia is loathe to cast Assad aside, even as relations between Moscow and Damascus have cooled.
Russian Foreign Minister Sergei Lavrov said: \"How exactly the work on a transition to a new stage is conducted will be decided by the Syrians themselves.\"
\"There are no demands to exclude from this process any one group. This aspect had been present in many of our partners\' proposals. We have convinced them that this is unacceptable,\" Lavrov said.
Chinese Foreign Minister Yang Jiechi also stressed that \"outsiders cannot make decisions for the Syrian people.\"
As divisions threatened to scupper talks earlier Saturday, Annan warned at the opening of the meeting that history would not look favourably on leaders who failed to chart a strategy to end the bloodshed in Syria.
A failure to unite also raised the spectre that the conflict that has claimed 15,800 lives over 16 months in the strategic Middle East country could spill over to the region and expose the world to fresh threats, said the former UN chief.
\"History is a sombre judge -- and it will judge us all harshly if we prove incapable of taking the right path today,\" Annan told the five permanent Security Council members -- the United States, Russia, Britain, China and France -- as well as regional powers Qatar, Turkey, Kuwait and Iraq.
Meanwhile fighting in Syria has only intensified in recent weeks as both government and opposition forces have received more weapons from their foreign backers.
The British-based Observatory warned of a \"catastrophic humanitarian situation\" in besieged Douma, which \"has been subjected to a fierce military campaign since June 21.\"
Violence has killed \"scores and wounded hundreds\" there since regime forces escalated attacks on the outlying suburb of Damascus, the group said.
\"More than 100 families remain in the town, unable to flee and forced to take refuge in shelters,\" it said.
While the violence rages there is also mounting concern about the destabilising impact it has on the region, in particular Jordan and Lebanon.
And the Turkish-Syrian border remains a potential flashpoint.
Turkey has sent tanks, troops and missile batteries toward the frontier, after Syria shot down a Turkish jet just over a week ago.
Meanwhile the head of the rebels\' Free Syrian Army told AFP that 2500 Syrian soldiers were \"massing 15km (10 miles) or slightly more from the Turkish border\" on Friday.
Egypt\'s President Mohammed Morsi -- elected after a revolution that overthrew strongman Hosni Mubarak -- on Saturday called for an end to bloodshed in Syria, in his inaugural address.
\"We support the Syrian people. We want the bloodshed to stop,\" he said.