Ahead of the official welcome gathering, British Prime Minister David Cameron and US President Barack Obama appealed to their colleagues to draw inspiration from Northern Ireland's efforts to reconcile British Protestants and Irish Catholics following decades of bloodshed.
Obama, flying into Belfast with his wife and daughters on Marine One, told an audience packed with 1,800 teenagers from dozens of largely segregated schools that Northern Ireland's young generation must take the lead in building on the UK region's US-brokered Good Friday peace accord of 1998.
Referring to Northern Ireland's ability to leave behind a four-decade conflict that claimed 3,700 lives, Cameron said leaders of the Group of Eight wealthy nations should be inspired by the setting a golf resort in the lush lakelands of County Fermanagh to deliver their own economic and peacemaking breakthroughs.
"Ten or 20 years ago, a G-8 in Fermanagh would have been unimaginable. But today Northern Ireland is a very different place ... A symbol of hope to the world," Cameron said.
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Those EU-US talks could start next month, with the end of 2014 a tentative goal for a deal that would lower prices on European and American imports and stimulate growth.
That's the easy part of the agenda. Later today over a working dinner, President Vladimir Putin and Russia's support for the Syrian government will be on the menu.
Cameron said he wanted the summit to deliver a firm plan for promoting multi-faction talks in Geneva. Moscow officially shares that goal but keeps shipping military aid to the army of Syrian President Bashar al-Assad.
Obama announced on Friday that the US would start sending weaponry, while Britain and France remained concerned that the firepower might end up helping anti-democratic extremists linked to Iran and Lebanon's Hezbollah militia.