ENNISKILLEN, Northern Ireland -- President Barack Obama and his Russian counterpart, Vladimir Putin, on Monday failed to resolve their significant differences over how to bring about an end to Syria's civil war, as each leader steps up military support for opposite sides in the worsening conflict.
Meeting for two hours on the sidelines of the Group of Eight summit, Mr. Obama and Mr. Putin discussed shared economic interests, the recent Iranian election and global security issues that have put the leaders at odds in the past. Syria's civil war was chief among them.
Sitting stiffly in side-by-side chairs, Mr. Obama and Mr. Putin each indicated that they still disagree over the war's preferred outcome, including on the future of President Bashar Assad and the goals of the armed rebellion.
"Our opinions do not coincide," Mr. Putin said. "But all of us have the intention to stop the violence in Syria."
Mr. Obama, speaking next, confirmed that "we do have differing perspectives" on the war and how to resolve it through negotiations that have yet to take shape.
Mr. Obama has demanded that Mr. Assad relinquish power as part of any negotiated peace settlement, a condition that Mr. Putin rejects. Russia is Mr. Assad's principal weapons supplier, and the Obama administration is about to begin arming rebels on the other side of the conflict that has killed 93,000 people over the past two years, according to U.N. estimates.
Little is known about some of the groups fighting Mr. Assad. There have been reports, supported by video, of atrocities carried out by some rebel factions. France and Britain, though, successfully sought to lift a European embargo on arms deliveries to the rebels. Mr. Obama, after months of deliberation, has decided to supply light weapons and ammunition to opposition forces, the White House announced last week.
But Mr. Putin warned that such a move was dangerous, saying after a meeting Sunday with British Prime Minister David Cameron that arming the rebels "has little relation to humanitarian values that have been preached in Europe for hundreds of years."
Western diplomats had given Mr. Obama little chance at the summit of changing Mr. Putin's opinion on Syria. But his inability to do so still posed an early setback for Mr. Obama on a three-day swing through Europe, his first to the continent since 2011. This time, he is facing rising skepticism in Europe over his expansion of drone warfare, recent disclosures about the National Security Agency's vast data-collecting efforts and his delay in more aggressively supporting Syria's beleaguered rebel forces.
Mr. Obama began meeting Monday with G-8 leaders near this picturesque town, hoping to mend fences and achieve a broader international consensus on how to improve the lagging global economy.
Hours before the summit, Mr. Obama and European leaders announced the start of negotiations to forge a new trade agreement between the United States and the 27-nation European bloc. The Transatlantic Trade and Investment Partnership would create what Mr. Cameron called "the biggest bilateral trade deal in history," although talks are expected to be complicated, despite urgency on both sides of the Atlantic to boost economic growth. The first round of negotiations will be held next month in Washington.
"There are going to be sensitivities on both sides, there are going to be politics on both sides," Mr. Obama said. "But I'm confident we can get it done."
Shadowing the summit's start Monday were new revelations that British and U.S. spy agencies monitored the emails and phone calls of foreign dignitaries at two international summits in London in 2009. The Guardian newspaper, citing documents it received from former National Security Agency contractor Edward Snowden, revealed the spying as the G-8 leaders gathered at the Lough Erne resort for a day and a half of meetings.
The disclosure follows recent reports in The Washington Post and the Guardian, also based on documents provided by Mr. Snowden, that disclosed widespread U.S. surveillance of phone and Internet use by ordinary citizens to detect patterns that could indicate terrorist activity.
The Guardian's latest revelations focused on two London summits in 2009 hosted by then-Prime Minister Gordon Brown. British intelligence agents, the newspaper said, went as far as setting up fake Internet cafes and tapping into cellular networks of diplomats and foreign officials.
On Monday, Mr. Cameron told Britain's Sky News that "we never comment on security or intelligence issues, and I am not about to start now." White House officials also declined to comment.
Mr. Obama began the day in Belfast, a city once defined by conflict and now living in uneasy peace. There, he urged Northern Ireland's youngest generations to reject the temptation of violence as, he said, technology and citizen activism are breaking down barriers in much of the world.
History colored Mr. Obama's remarks, which he delivered along the city's thriving waterfront 15 years after a peace accord ended decades of sectarian conflict between Catholic republicans seeking alliance with their southern neighbor and Protestants loyal to Britain.
Under a drizzling sky, teenagers in school blazers and ties lined up hours before the event outside Waterfront Hall for a chance to see Mr. Obama on his first visit to Northern Ireland. Mr. Obama told them to defend their fragile peace and to count on the United States when the Good Friday Agreement, brokered by former U.S. Sen. George Mitchell, D-Maine, is tested as it has been this year.
"The terms of peace may be negotiated by leaders, but the fate of peace is up to you," Mr. Obama told the audience.