He told reporters at U.N. World Headquarters in New York Tuesday the objective of the current review, "should be to strengthen the treaty and, in particular, to ensure that North Korea and Iran do not become nuclear powers."
"I believe there is a high probability that the conference will fail to achieve those objectives," he said.
McNamara, defense secretary under U.S. presidents John Kennedy and Lyndon Johnson, and the engineer of the war in Vietnam, said if Iran and North Korea continued on their paths, other nations will follow.
He said both nations fear Washington seeks a change in their leadership.
"It is inconsistent and ineffective to demand disarmament and pursue 'regime change' simultaneously," McNamara said, calling for negotiations with both North Korea and Iran.
McNamara said if the review conference fails, as he fears it will, the U.N. Security Council should step in and "take whatever action appears necessary to stop proliferation."