The trade summit was the latest to be marred by regional divisions over the issue.
A top negotiator who asked not to be identified told The Associated Press on Saturday that the summit's final declaration would present two opposing views.
One view supports the proposed Free Trade Area of the Americas (FTAA), while the other delays judgment on the issue until after World Trade Organisation (WTO) talks in December.
The decision came after hours of wrangling that delayed the summit's close for eight hours.
Almost all of the leaders - including US President George Bush - left during the discussions and put high-level negotiators in charge of resolving the prickly subject.
Mexico, the United States and 27 other nations wanted to set an April deadline for talks, but that was opposed by Brazil, Argentina, Uruguay, Paraguay and Venezuela.
The US says the trade zone would open up new markets for Americans while bringing wealth and jobs to Latin America, but Venezuelan leader Hugo Chavez came to the summit in this seaside resort vowing to "bury FTAA".
Protesters were opposed to
Bush's presence at the summit
The last-minute haggling at the summit of 34 Latin American and Caribbean nations came after Brazil - a key regional player with Latin America's largest economy - hedged at setting a firm date because it wants to focus for now on ongoing WTO talks aimed at cutting tariffs around the world and boosting the global economy.
"Anything we do now, before the WTO meeting, could confuse the facts and we'd be creating an impediment to the WTO," Brazil President Luiz Inacio Lula da Silva told reporters on the sidelines of the summit at Argentina's most renowned summer resort city Mar del Plata.
The city was calm on Saturday after protesters opposed to the FTAA and Bush's presence clashed in street battles with riot police, burning and ransacking businesses just 10 blocks from the theatre where the leaders opened the summit.
Chavez, easily the most vocal critic of the FTAA, declared the deal dead at a peaceful rally on Friday for more than 20,000 protesters.
On Saturday, Mexican President Vicente Fox expressed irritation with his Venezuelan counterpart, saying: "This is a personal position of the Venezuelan president."
The Mexican president also denied allegations by Chavez that Washington is trying to strong-arm the region into a free trade agreement.
"No one has ever been forced into a free trade deal"
"No one has ever been forced into a free trade deal," Fox said.
Chavez has said an anti-FTAA should be formed just for Latin America and the Caribbean based on socialist ideals.
Fox argued that the 29 countries that want to forge ahead should form the trade zone on their own - even though that would leave out Argentina, Brazil, Paraguay, Uruguay and Venezuela and dash hopes of creating a bloc that would eclipse the European Union.