Leaders from 34 American nations are preparing a final declaration to end their summit in Monterrey, Mexico.
But there are still disagreements among them, especially over a proposed free trade area for the Americas, for which the US has lobbied strongly.
Brazil, Venezuela and other nations do not want the issue mentioned in the document, saying it is not a solution to the region's deepening poverty.
Those present are also debating a wide range of social and security issues.
Correspondents say that even before the two-day summit began on Monday, the US and the region's left-wing leaders had struggled to agree on the agenda.
They say that US President George W Bush's fierce attack on communist Cuba under Fidel Castro has also proved to be a highly contentious issue, as several Latin American nations have good relations with Havana.
Cuba was not invited to the summit.
'New moral architecture'
"Over the long term, trade is the most certain path to lasting prosperity," President Bush said at the summit opening ceremony.
"Together we will... lift all our nations, and show the world that free societies and free markets can deliver real benefits to our citizens," he said.
But several Latin American nations challenged Mr Bush's belief that the planned Free Trade Area of the Americas (FTAA) will automatically bring prosperity to the region.
Peruvian President Alejandro Toledo criticised Washington for refusing to lower agricultural subsidies while asking the region's poor nations "to play ball in the free trade court".
His words were echoed by Venezuelan President Hugo Chavez who urged the establishment of "a new moral architecture" in the region that "favours the weakest".
Brazil and several other nations have already rejected the US effort to include in the final declaration a reaffirmation of the goal of finishing FTAA talks by 1 January 2005.
The FTAA aims to create the world's largest free trade area with a market of some 800 million people.
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