Venezuelan President Hugo Chavez says he will have to reassess ties with Colombia, which is set to allow the US to use its bases for anti-drug flights.
Mr Chavez, who already has difficult relations with Bogota and Washington, said an increased presence of US troops would be "a threat to Venezuela".
Colombia and the US are finalising an accord to make Colombia a hub for US anti-drug operations in South America.
Venezuela is Colombia's most important trading partner after the US.
President Chavez's comments echo statements by the Bolivian leader, Evo Morales, and Daniel Ortega of Nicaragua, condemning the imminent accord between Colombia and the US as "treason" and a threat to regional stability.
"Now the Yankees want to set up four more military bases in Colombia, of course they use euphemisms and say they aren't Yankee bases, but rather Colombian bases," said Mr Chavez.
He had instructed Venezuela's foreign minister "to review our relationship with Colombia," he said.
Bilateral trade amounted to more than $7bn (£4.3bn) in 2008, of which some $6bn comprised Colombian exports to Venezuela.
The Colombian government has difficult relations with several countries in the Andean region, including Ecuador, which recently imposed tariffs on Colombian exports.
Colombian President Alvaro Uribe, whose administration has been at pains to insist the accord would not infringe national sovereignty and will boost regional security, has said the agreement is "to strengthen Colombian military bases, not to open US bases".
"The accord is to recover the rights of Colombians to live in peace," he said.
Colombian officials have indicated that a deal is close with Washington to allow the US military to use its bases and airfields to gather intelligence and support operations against drugs production and terrorism.
The US was forced to look for a new centre for regional operations after Ecuador refused to renew the lease on its military base of Manta.
Details of the accord have not been disclosed but reports say the US would use at least three air bases. A maximum of 800 US military personnel and 600 civilian defence contractors would be based in Colombia.
This week a US congressional report said corruption in Venezuela's government and military was allowing drug trafficking into the US to flourish.
Mr Chavez dismissed the report as "a new lie" from the US.