President Uribe's deal with the US has caused concern in the region
Colombian opposition groups have reacted angrily after details of a controversial military deal with the US were made public.
Under the 10-year deal, the US military will not only have access to military bases, but also be able to use major international civilian airports.
US personnel and defence contractors will also enjoy diplomatic immunity.
President Alvaro Uribe says the agreement will help rid Colombia of drugs gangs and left-wing rebel groups.
But leading opposition senator Gustavo Petro, of the left-wing PDA party, said the deal amounted to a virtual US occupation of Colombia.
The accord was signed last Friday but full details were only made public on Tuesday.
They reveal that the US military will have access to seven Colombian army, navy and air force bases and also be able to use civilian airports under conditions that have still not been made clear.
Colombia's military commander, Gen Freddy Padilla, was quoted by national media as saying that the benefits of the agreement will be felt throughout the country as the US conducts anti-drug and anti-terrorist missions.
The deal has led to a worsening of already strained ties between Colombia and Venezuela.
Venezuela has broken off diplomatic relations with Bogota and Venezuelan President Hugo Chavez has warned that Colombian military bases could be used by the US to attack his country.
Other countries in the region, including Brazil and Chile, have also expressed concern.
The BBC's Jeremy McDermott, in Colombia, says Colombia is increasingly isolated in the region, but does not seem to care, just so long as it has US support.