South American leaders at a regional summit have expressed fresh concerns over Colombian plans to grant American troops access to its military bases.
But at thegathering in Ecuador, they rejected a proposal to formally condemn the proposals, which would allow US access up to seven Colombian bases.
Venezuelan President Hugo Chavez warned that "the winds ofwar were beginning to blow" across the region.
Colombia says it needs US support to tackle drug lords and left-wing rebels.
The US wants to relocate its base for anti-drug operations in Latin Americato Colombia, after Ecuadorean President Rafael Correa refused to extend an agreement allowing US access to a military base in Ecuador.
The Brazilian president, Luiz Inacio Lula da Silva -whose government had previously described the plans as a matter for Colombia - called for a meeting between US President Barack Obama and the region's leaders to discuss their concerns directly.
"Aspresident of Brazil, this climate of unease disturbs me," said Mr Silva, reports AP news agency. "I think we should directly discuss our discontent with the American government."
But during Monday'sUnion of South American Nations (Unasur) summit in the Ecuadorean capital, Quito, Mr Chavez led criticism of the Colombia-US accord.
The Venezuelan leader warned that the July agreement between Bogotaand Washington "could generate a war in South America".
BBC South America correspondent Candace Piette says that in a news conference at the end of their meeting, held in an ancient church in Quito,the 12 presidents looked uncomfortable.
Although a number of countries in the region had previously expressed alarm over the plan, the summit failed to back Venezuelan and Bolivian calls for a jointstatement condemning the move.
Instead, Unasur members agreed to hold talks - in Argentina later this month - to discuss the controversial Colombian-US proposal.
Colombian President Alvaro Uribe,...