James Comey, director of the US's Federal Bureau of Investigation, commended Spain on Monday for playing an “essential” part in stopping numerous terrorist attacks from taking place across Europe, the Middle East, Africa and Asia.
The FBI head met Spain's Interior Minister Jorge Fernández Díaz and National Police chief Ignacio Cosido on Monday to exchange information on terrorism, organized crime and cybercrime.
Details of their meeting and joint investigations have been summarized in a statement released by the US embassy in Madrid on Tuesday.
The communiqué highlights how the exchange of information between both countries prevented an Al-Qaeda plan to use drones to deliver explosives in Spain and Europe.
According to the US embassy, the "excellent" relations between Spain and US authorities also led to the arrest of four Mexican drug kingpins belonging to the Sinaloa cartel.
The news comes just weeks after Félix Sánz, head of Spain's National Intelligence Centre (CNI), admitted his organization had shared details of millions of telephone calls with the US.
Sánz vehemently denied this information related to Spanish citizens.
His words came in the wake of Spanish media allegations that US security services had tracked 60.5 million telephone calls in Spain in a single month, according to a leaked document by whistle-blower Edward Snowden.
Those media reports alleged the US had spied on Spain but the US responded by saying it was provided phone call data by Spain.