Malcolm Chalmers, deputy director-general of the Royal United Services Institute military think tank, told CBS News in March that about 20% of Ukraine's military hardware is supplied by the U.S., with 25% provided by Europe and the rest of the world, and 55% produced in Ukraine.

The move "was made to put America’s interests first," a White House spokeswoman said, as U.S. munitions have been depleted in recent years.