U.S. officials say the summit will focus on issues where the United States and Europe can cooperate -- issues like promoting freedom and democracy, and how to deal with Iran over its nuclear program.
But EU leaders are also expected to raise topics where there are sharp differences with Washington -- in particular, the detention camp at Guantanamo Bay.
The summit is seen as an opportunity for Washington and its European allies to confirm a mending of ties since strains over the U.S.-led invasion of Iraq.
Roses And Thorns
So, there were light-hearted pleasantries as Bush met first with Austrian President Heinz Fischer and the two men posed for photos between their two top diplomats, Austrian Foreign Secretary Ursula Plassnik and U.S. Secretary of State Condoleezza Rice.
"This is called 'thorns between two roses,'" Bush joked.
On June 15, Bush's national security adviser, Stephen Hadley, said the summit would focus on three areas where the United States and the EU could cooperate "to make a safer and better world."
"Promoting freedom and democracy, enhancing security, and pursuing greater global prosperity," Hadley said. "We are seeking to enhance cooperation in promoting democracy in the Middle East, Africa, Europe, and Latin America. On the security front, the leaders will set priorities for U.S.-EU counterterrorism cooperation, particularly countering terrorist financing and efforts to prevent terrorist access to weapons of mass destruction. Additionally, the [U.S.] president will discuss with his EU counterparts the way forward on Iran. The president believes that a united international front is the best way to encourage Iran verifiably to suspend its enrichment and reprocessing activities and return to negotiations. And if they do so, the United States will participate in those negotiations."
But some thornier issues are likely to come up at today's summit.
The EU wants Washington to extend its visa waiver to all EU member countries, and not just the old, pre-expansion ones.
There are also differences over trade, with the United States urging Europe to lower its protections for farmers.
But most of all, there's concern in Europe over the U.S. detention center for terrorism suspects at Guantanamo Bay in Cuba.
There have been growing calls for the United States to shut down Guantanamo, and this summit comes less than two weeks after three inmates committed suicide by hanging in their cells on June 10.
Elmar Brok is a European Parliament member who recently visited the prison. He says he hopes the summit will be instrumental in leading to Guantanamo's eventual closure.
"I think it's very important that the American side understands that we can win the fight against terrorism only if we stick to our own values, our own principles of rule of law," Brok said. "And if we give up that because of special reasons we lose credibility, and I hope we come closer together on that proposition."
Ahead of the summit, Luxembourg's Prime Minister Jean-Claude Juncker said EU leaders must use the meeting to call for the prison’s closure. Guantanamo, he told Germany's "Die Welt" newspaper, "is very bad for the image of the U.S."
News agencies say a draft summit declaration will address some of the EU concerns.
The two sides will reportedly vow to "ensure that measures taken to combat terrorism comply fully with our international obligations, including human rights."
(compiled from agency reports)
To view RFE/RL's archive of coverage related to EU expansion, click here .