Nearly 3,000 protesters blocked the streets in the city centre, waving banners reading "Bush Go Home" and chanting
slogans.

Bush is scheduled to arrive in Madrid on Tuesday to kick off a six-day tour of Europe.

The demonstrators were angry over U.S. embargoes against Cuba and Iraq, U.S. missile defence plans, the death penalty and Bush's decision to reject the Kyoto global warming pact.

Bush assembled a Cabinet-level working group on global warming in March, about two weeks after he backed away from a campaign pledge to regulate carbon dioxide emissions from power plants.

He then rejected an international pact negotiated in 1997 in Kyoto, Japan, requiring industrial nations to reduce
greenhouse gases by specified amounts.

Carlo Acero, Spanish environmentalist, said: "I am here because of this imperialist president who thinks the world is his garden... the world is bigger than the U.S."

On Tuesday night protesters are set to hold a second
demonstration in front of the U.S. embassy.

Organisers say they will do everything possible to keep the protest peaceful.

The World Bank recently cancelled a conference on poverty in Barcelona fearing confrontation from anti-globalisation groups.

Spanish officials said security would be tight during Bush's visit but that no "extraordinary" measures were being taken.