Most of the training, paid for in part by the United States, takes place in Mexico, but some Mexican soldiers and police officers are traveling to Colombia to train with battle-tested police commandos, the newspaper said.

"Mexico has what we had some years ago, which are very powerful cartels," said Colombian President Juan Manuel Santos. "What we can provide is the experience that we have had dismantling those cartels, training intelligence officers, training judicial police."

Engaging Colombian officials to train Mexican officers is a politically savvy way to improve Mexico's security forces without a visible U.S. military or police presence in Mexico.

"The American military can indirectly do a lot more through the Colombians than they politically would be able to do directly," said Roderic Ai Camp, an expert on Mexico's military at Claremont McKenna College in California. "Given the loss of half of Mexico's national territory to the United States in the 19th century, and the Mexican army's hesitant cooperation with their American counterparts, the Colombians are a logical proxy."