Throughout the past decades, Denmark had a very close cooperation with the US. This increased dramatically in the decade that came to be defined by the 9/11 attacks and the so-called global "war on terror".
US government documents leaked by Edward Snowden revealed that there are four levels of cooperation between US and foreign intelligence agencies. Denmark, along with Norway, the Netherlands, and France are in the second highest tier or the so-called "Nine Eyes".
Five Anglophone countries, the US, Australia, Canada, New Zealand, and the UK belong to the highest tier, "Comprehensive Cooperation", otherwise known as the "Five Eyes".