Why is China warning the UN of a Japanese ‘nuclear breakout’?

The row between China and Japan has ratcheted up a notch, with Beijing issuing a strongly worded position paper warning that Tokyo would soon be able to produce nuclear weapons.
In the document released on Thursday, China called on the United Nations to make Japan’s potential pursuit of nuclear arms an “important agenda item” at an ongoing convention at the organisation’s New York headquarters. China is a permanent member of the UN Security Council and will assume the monthly rotating presidency…