The Mayor of Quebec, Mr Jean-Paul L'Allier, was delighted when his walled Canadian city was chosen several years ago as the site of next week's summit of American leaders.

However, after seeing on television the violent clashes between police and protesters which disrupted the 1999 World Trade Organisation meeting in Seattle, he changed his mind. Mr L'Allier even tried to cancel the summit, which aims to establish a free trade area stretching from the Arctic to the Antarctic, but to no avail.

The meeting of 34 American presidents and prime ministers, including US President George W Bush, and 4,000 other delegates, will go ahead on April 20th-22nd - but behind a new Quebec wall.

A barrier of concrete and chain-link fencing five kilometres long and three metres high is being erected around the conference centre. It is designed to keep away thousands of trade unionists and social activists heading for the city to protest against an agreement they believe would favour corporate interests over people.

The main purpose of the Summit of the Americas is to form by 2005 a common market incorporating the 315 million inhabitants of North America and the 500 million people of Central and Southern America. It will be the biggest gathering ever of world leaders on Canadian soil.

In an attempt to defuse anti-globalisation protests which now regularly disrupt international trade gatherings, the Mayor has offered an area in the lower town more than a kilometre from the summit venue for an alternative people's meeting and concert.

Mr L'Allier said the city has learned from the Seattle experience, when police numbers proved inadequate, and will provide a large number of police, but with instructions to stay cool. Next weekend will in fact see the largest peacetime police operation in Canadian history. A total of 3,000 members of the Royal Canadian Mounted Police (RCMP), 2,000 provincial police and 1,000 local city and borough police will be deployed to separate the dignitaries from an expected 10,000 demonstrators.

The security forces have been told not to clash with the crowds except in defence of private property, the mayor said. The police say, however, that there is a real threat of violence at the Summit of the Americas and they will be prepared for trouble.

"There are groups who have planned very precise actions that we know about for the most part," said Florent Gagne, director-general of the Surete du Quebec, the Quebec Province police force. "They want to prepare spectacular acts to get international attention from the press."

Canadian immigration officials have been stopping known anti-globalisation demonstrators from crossing the border into Canada. In anticipation of an unruly weekend, 579 male and 45 female inmates of Quebec City Provincial Gaol have been moved elsewhere to provide holding cells.

To the dismay of protest organisers a RCMP officer, Staff Sergeant Hugh Stewart, who shot to national notoriety for his use of pepper spray on passive demonstrators during protests at the 1997 APEC summit in Vancouver - earning him the nickname Sergeant Pepper - has been assigned to the front line of the police, according to the Toronto Globe and Mail.

Observers believe that intense anger in the international community over President Bush's opposition to the Kyoto agreement against global warming could translate into a strong anti-US mood and raised tempers on the streets of Quebec.

There is also dismay on the left at the exclusion by Canadian Prime Minister Jean Chretien of President Fidel Castro of Cuba. A leaked draft declaration prepared form the summit included a clause inserted by Canada that would make it a democrats-only club.

Anti-summit activists argue that by favouring the interests of multinationals over citizens and their governments, free trade lessens democracy and drives more people into poverty. Graffiti has appeared in Quebec stating, "Le Pouvoir au Peuple, pas aux Multinationals".

Rieky Stuart of the aid organisation Oxfam said Haiti had the most free trade regime in South America but was the poorest country because when it opened its markets to cheap US rice, Haitian farmers were driven into bankruptcy and forced to live in slums.