Trying to build a new consensus among allies, President Bush opened a European trip Friday with expectations that NATO (search) will shoulder heavier responsibilities in Iraq.

The next five days are all about summitry — the U.S.-European Union summit this weekend in Ireland and the NATO summit in Turkey (search) next week. Allied leaders are expressing a new willingness to help in Iraq, although not at the levels once anticipated.

EU External Affairs Commissioner Chris Patten (search) told reporters shortly after Bush arrived here on Friday that persistent violence could cause Iraq to unravel.

"All of us in the international community are worried that the violence directed against moderate leadership in each of the communities and directed against attempts at long-term, sustainable reconstruction ... could lead to Iraq flying apart in the next few months," Patten said. He added that while the EU is "absolutely determined" to help reconstruct Iraq and ensure that elections are held, violence could derail those goals.

Some European leaders worry that they will lose political capital back home if they appear too cozy with Bush.

"America has never been at a lower point in the minds of citizens around the world," says Thomas Mann, a political analyst at Brookings Institution, a liberal-leaning think tank. "Our relations with other countries, including natural allies, have seldom been as strained. To be associated with President Bush and current American policy is a political liability around the world right now."

Police and troops shut down roads and erected barbed-wire barricades Friday to deter protesters from interrupting the summit between Bush and European Union leaders. Thousands marched through Dublin, the Irish capital, denouncing Bush as a warmonger and urging that facilities for American military flights be withdrawn from Shannon Airport, a strategic refueling point used by thousands of U.S. troops each month.

"Sadly, there's no great welcome for President Bush," said the Rev. Tom Ryan, a Catholic priest in the town of Shannon. "The vast majority of people would not agree with the policies of the American government or President Bush."

Protests are expected in several European cities this weekend. Left-wing activists planned protests in Dublin on Friday night and the summit venue Saturday. The protesters want Ireland to stop allowing U.S. military planes to land at Shannon airport, a strategic refueling point en route to Iraq. Protests are expected in several European cities this weekend.

Topics at both summits will range from Afghanistan to counterterrorism, from trade to curbing the spread of nuclear weapons. But Iraq will be at the forefront.

Bush, who is seeking allies' help in Iraq, will be holding out one hand and carrying what he believes is a persuasive argument in his pocket — one that asks NATO members to look in their own history books.

On Saturday in Ireland, Bush meets with Prime Minister Bertie Ahern, currently the head of the European Union, and President Mary McAleese before the start of the U.S.-EU summit. He'll meet later Saturday with business leaders.

In an interview with Turkey's private NTV television before he left Washington, Bush acknowledged it was unlikely that NATO countries would contribute additional troops to Iraq, but said he was hopeful some would help train Iraqi forces.

Bush also pledged to help Turkey and Iraq crack down on Turkish Kurdish rebels seeking autonomy from Turkey. He was speaking on the eve of a weekend visit to Turkey ahead of Monday's NATO summit meeting in Istanbul. Both France and Germany have resisted a NATO mission in Iraq.

"This is about the spread of freedom and liberty," Bush's national security adviser, Condoleezza Rice, said Thursday in explaining the message Bush will carry to Europe. "That's what NATO has stood up for from the very beginning. ... Many of the members of NATO would not be free and at liberty themselves had it not been for the sacrifices of others, including sacrifices of the United States."

In an interview Thursday with Ireland's RTE television, Bush defended his decision to invade Iraq and insisted most of Europe backed the move. He also disputed the interviewer's assertion that most Irish people thought the world was more dangerous today than before the Iraq invasion.

"What was it like Sept. 11, 2001?" he retorted. "I wouldn't have made the decisions I did if I didn't believe the world would be better. Why would I put people in harm's way if I didn't believe the world would be better?"

The White House emphasizes that 16 NATO nations already have forces in Iraq, and some members of the alliance say they're willing to help train Iraqi security forces. Major NATO powers such as Germany and France have emphatically declined to send troops.