US President Barack Obama sparred with Russia's Vladimir Putin over how to end the war in Syria on Monday during an icy encounter at a G8 summit where divisions over the conflict eclipsed the rest of the agenda.

US President Barack Obama meets with Russian President Vladimir Putin during the G8 Summit at Lough Erne in Enniskillen, Northern Ireland June 17, 2013. [Agencies via China Daily]

Speaking after talks with Obama, Putin said Moscow and Washington had differing views over Syria but agreed the bloodshed must stop and that the warring parties should be brought to the negotiating table.

Both leaders looked tense and uncomfortable as they addressed reporters after about two hours of talks, with Putin staring mostly at the floor as he spoke about Syria and Obama only glancing occasionally at the Russian leader.

"Our positions do not fully coincide, but we are united by the common intention to end the violence, to stop the number of victims increasing in Syria, to resolve the problems by peaceful means, including the Geneva talks," Putin said.

"We agreed to push the process of peace talks and encourage the parties to sit down at the negotiation table, organise the talks in Geneva."

Obama tried to lighten the mood at the end of the talks by bringing up the subject of judo, but Putin, a black belt in the martial art, parried by saying the U.S. president was just trying to get him to relax.

"We compared notes on President Putin's expertise in judo and my declining skills in basketball," Obama said. "We both agreed that as we get older, it takes more time to recover."

Putin replied coldly: "The president wants to relax with his statement of age."

Divisions over Syria dominated the atmosphere as global leaders descended on the remote golf resort in Northern Ireland, a place once rocked by decades of violence but which Britain now wants to showcase as a model of successful conflict resolution.

Speaking alongside Putin after their first face-to-face meeting in a year, Obama said the two men had different views on Syria but shared an interest in stopping violence and ensuring chemical weapons were not used.

"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.

He added the two leaders had instructed their teams to work on a peace conference about Syria in Geneva. The United States said last week it would step up military aid to the rebels including automatic weapons, light mortars and rocket-propelled grenades.

Overcoming mistrust

After a day of intense talks, leaders later retreated to a lodge on the shore of Lough Erne where they held further talks over a dinner of crab, fillet of beef, and whisky-laced custard.

British Prime Minister David Cameron, who is chairing the summit, hopes to forge a G8 consensus on specific issues regarding Syria including humanitarian aid but sought to avoid broaching the divisive subject of arming rebels since there was no consensus on the issue, officials said.

Despite the obvious tensions, Moscow and the West have been trying to stress they are genuinely trying to overcome mistrust and find a way forward. They had earlier agreed to call a Syrian peace conference in Geneva although progress has been slow.

"We know we do not agree with Putin on arms supplies, chemical weapons and relations with the Syrian regime. So what we need to do...is to move towards a political solution via the Geneva conference," French President Francois Hollande told reporters after separate talks with Putin.

German Chancellor Angela Merkel echoed the view, though Canadian Prime Minister Stephen Harper earlier struck a tougher tone, saying Putin was supporting thugs in Syria.

Syria aside, Cameron wants to focus the formal agenda on tax, trade and transparency, dubbed "The Three Ts", topics expected to dominate discussions on Tuesday.

As the summit kicked off on Monday afternoon, the United States and the EU opened negotiations for the world's most ambitious free-trade deal, promising thousands of new jobs and accelerated growth on both sides of the Atlantic.

The global leaders, representing just over half of the $71.7 trillion global economy - also discussed global economy and urged the euro zone to press on with a banking union and Japan to follow up on massive central bank stimulus with structural reforms and measures to tackle its budget deficit.

Yet, Syria dominated news headlines. In some of his most striking remarks, Putin described rebels as cannibals who ate human flesh and warned of the dangers of giving guns to such people.

Assad himself waded into the dispute, saying Europe would "pay the price" if it delivered arms to rebel forces.

"Terrorists will gain experience in combat and return with extremist ideologies," he said in an advance extract of an interview due to be published in the Frankfurter Allgemeine Zeitung on Tuesday.