Security is extremely tight in Northern Ireland as leaders from the world's eight most powerful nations gathered at a lakeside golf course.
There were fissures among the three Western nations, despite their shared belief that Assad must leave power. Britain and France appear unwilling - at least for now - to join President Barack Obama in arming the Syrian rebels, a step the U.S. president reluctantly finalized last week.
The debate over Syria's two-year conflict loomed large as the two-day summit of the Group of 8 industrial nations opened Monday at a lakeside resort in Northern Ireland. The lack of consensus even among allies underscored the vexing nature of the conflict in Syria, where at least 93,000 people have been killed as rebels struggle to overtake Assad forces buttressed by support from Hezbollah, Iran and Russia.
Obama and Putin, who already have a frosty relationship, did little to hide their differing views on the matter while speaking to reporters following a one-on-one meeting on the sidelines of the summit Monday evening. The two-hour meeting marked the first time the two leaders have met in-person since last year.
"We do have different perspectives on the problem," Obama said plainly of their divergent views on Syria.
The Russian leader, speaking through a translator, agreed, saying, "our opinions do not coincide."
But despite their seemingly intractable differences, Obama and Putin did express a shared desire to stop the violence in Syria and convene a political conference in Geneva, Switzerland, next month. But it's unclear who would participate in such a meeting or whether the rebels, given their weakened position, would have any leverage if they did.
Top European Union official Jose Manuel Barroso says talks on a sweeping new free trade agreement between the EU and the U.S. will begin in July.
Barroso, head of the EU's executive arm the Commission, says that the deal could offer "huge economic benefits" for both sides of the Atlantic.
Mr. Obama added a deal would be "a priority of mine" and that he was "confident we can get it done."
Negotiations would focus on lowering tariffs and rules that hinder the trade of goods and services and is seen as a way of promoting new growth and jobs amid an uncertain global recovery.
British Prime Minister David Cameron said he expects a formal agreement to launch negotiations on a European-American free trade agreement. He said a pact to slash tariffs on exports would boost employment and growth on both sides of the Atlantic.
"This will be a summit that will drive growth and prosperity all over the world," Cameron declared as he arrived at the summit venue ahead of leaders from the United States, Canada, Russia, Germany, France, Italy and Japan as well as the 27-nation European Union.
Cameron says he also hopes to achieve agreement that no G-8 member should pay ransoms to secure the release of hostages in North Africa, where western and Asian workers are top targets for kidnappers.
More than 3,500 officers from Britain have been brought in to double security. British Army engineers have helped to erect a perimeter of steel fences and coiled razor wire for miles around the summit's only road entrance.
President Barack Obama and his family arrived in Northern Ireland Monday as the G-8 summit got under way. Mr. Obama, first lady Michelle and their daughters Malia and Sasha arrived on an overnight flight.
Air space over much of Northern Ireland is also being restricted to summit traffic for the duration of the summit, which concludes Tuesday. And the water around the resort's peninsula has been similarly closed to civilians, with police patrolling by boat, although the public is still free to fish from shore.
As the summit commenced, NSA leaker Edward Snowden told the Guardian that the British agency GCHQ repeatedly hacked into diplomats' phones and emails when the U.K. hosted the 2009 G-20 summit in London.
The Guardian cites several internal government documents provided by former National Surveillance Agency contractor Edward Snowden as the basis for these new allegations. The documents also reportedly show that the NSA tried to eavesdrop on Russian leader Dmitry Medvedev as he telephoned back to Moscow via satellite. The NSA is the GCHQ's sister organization in the U.S.
The Associated Press and ABC News contributed to this report.