Regional concerns

The deal has been criticised in countries across Latin America as a method for the US to expand its sphere of influence across the region. Lula said last week that he was suspicious of the US-Colombia deal.

"Some of Colombia's friends are worried by the [US] bases, because it could be the first step for a war in South America … It's about the Yankees, the most aggressive nation in history"

Hugo Chavez, Venezuela president

Jim Jones, the US national security adviser, acknowledged that countries across South America had concerns over the agreement.

"There is no magic, nothing secret under the table," Jones said.

"Just to make sure, we will send a military briefing team around to interested countries in the region to make sure everybody understands what this is and what this is not."

Uribe was booed on Wednesday by a small crowd of people protesting against the agreement as he arrived at the La Moneda palace in Chile to meet President Michelle Bachelet, who declared the deal a matter of Colombia's national interest.

He then headed to Argentina to hold talks with President Cristina Fernandez. Speaking briefly after the meeting, he said it was "wide-ranging and covered important themes", before heading to Uruguay on the next stop on his tour.

Peru supportive

Fernandez told Uribe that "conflict in the region must be lowered," and a base deal with the US "does not contribute toward that goal", according to quotes published by Telam, the Argentine state news agency.

However, Uribe was given support in Peru, where Alan Garcia, the Peruvian president, said that Colombia was taking a strong democratic lead.

Uribe has avoided direct talks with the presidents of Ecuador and Venezuela, who are both strongly opposed to the deal.

Hugo Chavez, Venezuela's president, said on Thursday that the deal allowing the US military's use of Colombian bases was provocative.

"Some of Colombia's friends are worried by the [US] bases, because it could be the first step for a war in South America … It's about the Yankees, the most aggressive nation in history," he said.

The president of Bolivia, one of Chavez's strongest regional allies, said that the deal had nothing to do with cracking down on drug smugglers or armed groups in Colombia.

"It is for the region - and that's why we have the obligation to tell the truth, to defend the dignity not just of the Bolivians, but of South America," Evo Morales said on Wednesday.