Following an icy encounter between the Kremlin chief and U.S. President Barack Obama late on Monday, the G8 leaders will seek to find resolution to a war that has prompted powers across the Middle East to square off on sectarian lines.
The sticking point again will be Putin, who faced a barrage of criticism from Western leaders for supporting Assad and the Syrian's president's attempt to crush a 2-year-old uprising in which at least 93,000 people have been killed.
"It's a clarifying moment to see what kind of commitments the Russians are willing to make in a leading world forum," a British official said before the leaders met for dinner at a remote, heavily guarded golf course outside of Enniskillen.
An official close to one of the delegations said the talks over dinner had gone better than expected and that a joint communiqué with Russia on Syria now seemed more likely. However, the official declined to speculate on what Russia might be willing to sign up for.
But if consensus could not be reached, it was possible a final statement at the end of the two-day summit might be released without Russia's input and in the name of the G7 rather than the G8.
Divisions over Syria dominated the atmosphere as global leaders met in Northern Ireland, a place once rocked by decades of violence but which Britain now wants to showcase as a model of conflict resolution.
Putin and Obama appeared tense as they addressed reporters late on Monday after about two hours of talks, with Putin mostly staring at the floor as he spoke about Syria and Obama only glancing occasionally at the Russian leader.
Stung by recent victories for Assad's forces and their support from Hezbollah guerrillas, the United States said last week it would step up military aid to the rebels, including automatic weapons, light mortars and rocket-propelled grenades.
Putin said Moscow and Washington had different views on Syria but agreed the bloodshed must stop and that the warring parties should be brought to the negotiating table.
"With respect to Syria, we do have differing perspectives on the problem but we share an interest in reducing the violence and securing chemical weapons and ensuring that they're neither used nor are they subject to proliferation," Obama said.
British Prime Minister David Cameron, who is chairing the summit, will on Tuesday seek to move the conversation on to taxation and how the Group of Eight leading nations can help close international loopholes in what has become a central theme for the British prime minister.
Cameron has been stung by revelations that the likes of Google and Starbucks have sharply cut their corporate tax bills in Britain using legal loopholes.
Last week he sought to turn up the pressure on other rich economies by pressing Britain's overseas tax havens into a transparency deal and announcing new disclosure rules for British firms.
Also on the agenda will be a drive by the British to secure a commitment from all the G8 leaders that they will no longer pay a ransom to kidnappers as part of an early meeting between the leaders about counterterrorism.