"[Russian] nuclear capability is significant, they have reorganized their conventional capability, their special operations capability. So Russia bears close watching and that is why I said they are the number one threat to the United States," Milley said at a Defense One conference in Washington, DC.
Milley added that the threat posed by Russia is a combination of overall military capabilities, and the intent to use those capabilities.
"It is very difficult to define future intent," Milley said of Russia after referring to Russian behaviour as "aggressive, not just assertive."
During his US Senate confirmation hearing in July, Milley again cited Russia as the top threat to the United States.
Russia's Foreign Ministry has repeatedly warned that US’ and NATO’s armament gathering and exercises along Russia’s borders are provocative actions and could undermine the region's stability. Moreover, Russia has also voiced concern over US plans to deploy parts of its missile defense shield to Europe.