Inside Story The United Nations chief warns of the waning influence of the global agreement. The Nuclear Non-Proliferation Treaty is the most extensive arms-control agreement in the world. It has 191 signatories and is based on a simple principle: Countries without nuclear weapons won’t acquire them, and those that do will give them up. Recommended Stories list of 4 items list 1 of 4 Photos: Chornobyl’s ‘liquidators’ return 40 years after nuclear disaster list 2 of 4 40 years since the world’s worst nuclear disaster in Ukraine list 3 of 4 The war on Iran is eroding nuclear non-proliferation list 4 of 4 The Process of Uranium Enrichment end of list But in recent years, implementation of the treaty has flagged. Both experts and diplomats are warning that the risk of a nuclear arms race has never been so high, and the head of the United Nations has issued warnings about the waning influence of the global agreement.…