The United States joined 33 other Western Hemisphere nations Sunday in pledging to establish a free-trade zone within four years and to limit membership in the agreement to democratic governments. 

The agreement was the result of a three-day summit, held in Quebec City, Canada, that brought the leaders of 34 North and South American and Caribbean nations together to discuss The Free Trade Area of the Americas. 

In their final statement, President Bush and the 33 other nations signed an agreement pledging to finish negotiations on the zone by January, 2005 and to open their markets by the end of that year. 

The treaty would create a barrier-free trade zone from the Arctic to Argentina, linking markets of 800 million people and economies ranging from the world's largest — the United States — to some of its tiniest. 

In the statement, the nations insisted that democracy was "fundamental to the advancement of all our objectives," adding that any "unconstitutional alteration or interruption of the democratic order ... constitutes an insurmountable obstacle" to participation in further hemispheric trade talks. 

The leaders signed the document in pairs, sitting down at a table two at a time to scrawl their names as Canadian Prime Minister Jean Chretien, the summit host, watched over their shoulders like a proud parent. 

The leaders said they would "conduct consultations" if any member state had a disruption of its democratic system, but the wording stopped short of establishing specific penalties or automatic expulsion from the talks on the Free Trade Area of the Americas. 

Chretien had heralded the democracy clause on Saturday as a pillar for the region's unity and prosperity in the future. 

Even Venezuela's populist Hugo Chavez — who staged a failed coup as a young lieutenant colonel in 1992 — told reporters Sunday that his country would sign the declaration despite reservations. 

"In Venezuela's case, representative democracy has been a trap that almost led the country to bloodshed," he said. "Some barons who were elected felt that they had a blank check to rob, betray and steam-roll others." 

With the signing of the democracy clause, Chretien singled out Haiti for its flawed election. 

"Democracies in certain countries continues to be fragile," Chretien said. He called on Haiti's president, Jean-Bertrand Aristide, to live up to promises he made to advance democracy in the island nation and said an official from the Organization of American States would travel to Haiti to observe whether such steps were being taken. 

Aristide, who became Haiti's first freely elected president in 1990, fell to a military coup and was restored to power in a 1994 U.S. invasion. He stepped down in 1996 and became president again last year in elections boycotted by the opposition because of a fraudulent legislative vote. 

Aristide pledged cooperation Sunday, but gave no indication of how he plans to address demands for new elections. 

"I am confident that we will come out with a quick resolution to the crisis in the next few days, thanks to the help of the Organization of American States," Aristide said. 

The so-called "democracy clause" excludes any country that ceases to be a democracy from participation in future summits, membership of the Free Trade Area of the Americas and the benefits of the Inter-American Development Bank, a key regional financier, Chretien said. 

The idea is to strengthen multiparty systems that have replaced military and civilian dictatorships across the region over the past two decades but have appeared increasingly shaky in some countries as economic prosperity has failed to follow. 

Cuba was the only country in the region excluded from the Quebec summit, for its lack of free elections. 

The declaration said the next Summit of the Americas would be in Argentina, but no date was provided. 

Poverty Clause 

The impact of unrestricted trade on poorer nations, one of the issues that brought 30,000 protesters to Quebec for the summit over the weekend, was also addressed in the agreement. 

Mindful of the economic inequalities of the region, the leaders committed themselves to halving the number of people living in extreme poverty by the year 2015. However, no plan for achieving that goal was outlined in the agreement. 

"We will spare no effort to free our fellow citizens from the dehumanizing conditions of extreme poverty," they said in their declaration. 

That responded to some of the demands of some of the protesters, but not all. While the majority of demonstrators marched peacefully through the city, about 2,000 battled with riot police along the 2.3-mile concrete-and-wire security wall erected around the summit venue. 

The leaders also were to release a draft text of the free-trade accord, meeting a key demand of citizens' groups and other protesters. 

But it was unlikely to appease the more radical, rock-throwing protesters intent on tearing down the summit perimeter fence. Those protesters have clashed with nightstick-wielding riot police who responded with water cannons, tear gas and rubber bullets. 

More clashes occurred overnight, with protesters setting fires and smashing windows in an area near the riverfront. Police said about 15 businesses complained of vandalism and minor theft, but there was no sign of widespread looting. 

Streets were quiet on a rainy Sunday morning, but security remained tight in case of more protests. 

Police said nearly 30,000 marchers processed through Quebec City on Saturday, with a few thousand growing violent along the security fence. 

Protests continued into the night and a stinging mist of tear gas settled on the city as the leaders and their spouses gathered at the Congress Center for dinner and entertainment. 

U.S. Secretary of State Colin Powell, a former general, told reporters he wasn't bothered by the fumes: "It didn't affect me, but an old infantryman always remembers what tear gas and pot smell like when you walk into the barracks." 

The Associated Press contributed to this report