Supporters of the withdrawal argued that it was a necessity in order to test and build a limited National Missile Defense to protect the United States from nuclear blackmail by a rogue state. The withdrawal also had many critics. John Rhinelander, a negotiator of the ABM treaty, predicted that the withdrawal would be a "fatal blow" to the Non-Proliferation Treaty and would lead to a "world without effective legal constraints on nuclear proliferation." The construction of a missile defense system was also feared to enable the US to attack with a nuclear first strike. Former U.S. Secretary of Defense William Perry also criticized the U.S. withdrawal as a very bad decision.