Updated

Former U.N. secretary-general Ban Ki-moon says the risks of nuclear conflict "are higher than they have been in several decades" and it's past time for the five nuclear powers to take steps toward disarmament.

Ban warned the Security Council on Wednesday that the failure of the U.S., Russia, China, Britain and France to make progress on disarmament risks undermining the Nuclear Nonproliferation Treaty. The NPT is the world's single most important pact on nuclear arms, credited with preventing their spread to dozens of nations since entering into force in 1970.

It has succeeded in doing this via a grand global bargain: Nations without nuclear weapons committed not to acquire them; those with nuclear weapons committed to move toward their elimination; and all endorsed everyone's right to develop peaceful nuclear energy.