The DEA agent said Costa Rica for many years was used as a transshipment point for drugs, "but in the past year-and-a-half to two years, most of the drugs belong to the Sinaloa cartel."

Headed by Joaquin Guzman, who broke out of a Mexican prison in 2001, the Sinaloa is considered Mexico's most powerful drug cartel. It has set up "bases here... and they're sending Costa Rican drugs from storage depots" to the United States, Springer said.

Springer's comments coincide with San Jose's request that Congress renew a six-month permit for US Navy ships to use its ports both to rest their crews and as part of a regional anti-drug trafficking effort.

It also comes amid Costa Rica's simmering border dispute with Nicaragua over a stretch of the San Juan river that serves as border between the two countries, in a jungle region local newspapers on Monday said is controlled by drug traffickers.

Costa Rica since 1948 has been constitutionally without a military. Security Minister Jose Maria Tijerino on Monday denied the press reports, but warned Costa Rica has the right to request foreign military assistance to deal with Nicaragua.

"Costa Rica is under attack, so it is fully justified should it seek help from friendly nations," the minister told a press conference.

Costa Rica accuses Nicaragua of occupying a river island and of illegal dredging operations. Managua has rejected an Organization of American States call for it to withdraw its troops from the area and has appealed to the International Court of Justice.

Costa Rican experts said Mexican drug traffickers are extending their tentacles across Central America to take control of all cocaine shipment routes from South America to the United States.

They fear the Sinaloa cartel will bring to Costa Rica all the rivalry and bloodshed of Mexico's drug cartel wars, which have killed more than 28,000 people since 2006 despite a government crackdown with 50,000 troops across the country.