A woman at the rally, Carmen Inturias, explained why she attended the rally in repudiation of Bush.
"North America for the North Americans, South America for the South Americans"
Hugo Chavez, president of Venezuela
She said: "Bush is always against the poor. Chavez is always for the poor."
Chavez was the only speaker at the event, which lasted nearly two hours.
Across the river border in the Uruguayan capital, Montevideo, a rowdy group of anti-American demonstrators scuffled with bystanders and shattered windows at an American fast-food restaurant. The incident underscored tensions there as Bush arrived on Friday night from neighbouring Brazil and was driven in a bullet-proof limousine to his hotel.
"Exterminate the Empire!" a masked woman spray-painted on a business facade in Montevideo. But there were no reports of serious injuries as the visit began with Uruguay's first left-wing president, Tabare Vazquez, who seeks greater trade with Washington.
Latin America tour
Chavez said Bush's five-nation tour would fail to improve America's image and dismissed his pledges of US aid as a cynical attempt to "confuse" Latin Americans.
On Argentine state television, the Venezuelan leader on Friday, said: "It seems he's just now discovered that poverty exists in the region".
|Hugo Chavez delivers a speech during a rally held against George Bush in Buenos Aires [AFP]|
At the stadium rally, about 20,000 people, including men and women with children in tow, applauded Chavez.
Claudio Hernandez, a Chilean, said: "We are here to show our support of Chavez and our repudiation of Bush and imperialism. We are against Bush because of his oil wars and his other policies."
Anti-American and anti-Bush sentiments run high in the countries on Bush's tour, particularly over the war in Iraq and US trade negotiations.
During his first stop in Sao Paulo, Brazil, riot police fired tear gas and clubbed some protesters after more than 6,000 people held a largely peaceful protest march on Thursday.
In Asuncion, Paraguay, a few dozen pro-Chavez supporters turned up outside the US embassy in that capital to protest against Bush on Friday - even though the US chief was not stopping there.
In Argentina, many still blame Washington for tolerating the country's brutal military regimes of 1976-1983, when thousands of dissidents were tortured and killed.
The organisers of Chavez's rally included Mercedes Merono of the Mothers of the Plaza de Mayo, a group still searching for sons and daughters who vanished after being arrested under military rule.
Merono said: "This counter-rally is extremely important. Bush seeks to take advantage of Latin America while Chavez supports the region's independence."
|Sao Paulo's military police on Thursday took|
action against anti-Bush demonstrators [AFP]
Police put down violent protests in Colombia in advance of Bush's visit there, and in Guatemala, Mayan leaders announced that Indian priests will purify the sacred archaeological site of Iximche to eliminate "bad spirits" after Bush visits there on Monday.
Juan Tiney, a Guatemalan activist, said: "That a person like [Bush], with the persecution of our migrant brothers in the United States, with the wars he has provoked, is going to walk in our sacred lands, is an offence for the Mayan people."
Bush wraps up his trip next week in Mexico, where a handful of protesters demonstrated on Friday outside the US embassy.