Bush will meet with more than two dozen European leaders during a tour aimed at healing the trans-Atlantic rift that opened during his first term, notably over the Iraq war (search).
"He is coming to persuade and influence the European leaders. We are afraid the European leaders will distance themselves from their people," said Pol de Vos, one of about 700 anti-Bush protesters marching peacefully in downtown Brussels.
Police have mounted an unprecedented security operation for the visit, deploying 2,500 officers — 1,000 more than usually deployed for the three or four summits that bring European Union leaders to the Belgian capital each year.
An alliance of 88 environmental, human rights, peace and other groups have planned protests near the U.S. Embassy for Monday and near the EU headquarters on Tuesday.
The Web site of the 'Stop Bush' alliance accused Bush of "crimes against humanity," saying he undermines international law and is an obstacle to the fight against global warming.
European leaders say they are keen to narrow the gap with Washington on Iraq and other contentious issues.
In his weekly radio address Saturday, Bush said he doesn't believe the West is split between an "idealistic United States and a cynical Europe ... America and Europe are the pillars of the free world."
"Leaders on both sides of the Atlantic understand that the hopes for peace in the world depend on the continued unity of free nations," he said. "We do not accept a false caricature that divides the Western world between an idealistic United States and a cynical Europe."
Iraq will be a top agenda item. The United States wants to see a larger international role in Iraq, particularly in training the country's military and police.
On Monday, European foreign ministers are to announce the opening of an EU office in Baghdad to oversee a democracy-building program that will train hundreds of Iraqi judges and prosecutors.
The 25-nation EU plans to train more than 700 judges, prosecutors and prison guards outside Iraq and provide euro2.34 million (US$3 million) for the Baghdad office that will recruit Iraqis and have a staff of about five.
On Monday, Bush meets with Belgium's King Albert II at the Royal Palace and with Prime Minister Guy Verhofstadt before giving a speech on trans-Atlantic relations. In the evening, he is to dine with French President Jacques Chirac, who was a leading opponent to the war in Iraq.
Bush will have breakfast with close ally British Prime Minister Tony Blair on Tuesday, before meeting the leaders of NATO's 26 member nations at the alliance's headquarters on Brussels' northeastern outskirts.
In the afternoon, he moves across town to meet with the 25 EU leaders, followed by a dinner with European Commission President Jose Manuel Barroso, foreign policy chief Javier Solana, EU Security Affairs and External Relations Commissioner Benita Ferrero-Waldner and Luxembourg Premier Jean-Claude Juncker, whose country currently holds the EU's rotating presidency.
Bush will then travel to Germany on Wednesday, before heading to Slovakia for a meeting with Russian President Vladimir Putin.