Drug trafficking, cyber attacks, intelligence sharing and border security are some of the issues MacKay has discussed with U.S. Defence Secretary Leon Panetta and Mexico's Secretary of National Defence, Gen. Guillermo Galvan Galvan.
Defence officials say the three defence officials are expected to announce new measures today to support the fight against narcotics.
MacKay's communications director, Jay Paxton, says the objective is to co-ordinate security to "assist the ongoing counter-narcotics strategies in our countries."
The so-called war on drugs has many critics, but U.S. government officials stress that the bold firepower of drug cartels means no one country or agency can go it alone.
The United Nations estimates that the drug trade in the United States, Canada and Mexico is now worth at least $147 billion a year.
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