The United Arab Emirates has quite close and friendly with the US, being described as the United States' best counter-terrorism ally in the Gulf by Richard A. Clarke, the U.S. national security advisor and counter-terrorism expert. In terms of defense, the United Arab Emirates Armed Forces has been nicknamed "Little Sparta" by United States Armed Forces generals and former U.S. Secretary of Defense James Mattis for its active role against extremists in the Middle East. The United Arab Emirates also hosts the only United States border preclearance in the Middle East.