Democratic U.S. presidential nominee Hillary Clinton said in a private speech to bankers three years ago that she would "ring China with missile defense" if Beijing failed to curb North Korea's nuclear ambitions, while also blasting "nationalist forces" in Japan for stoking the Senkaku row, a hacked email has shown.

The excerpts from a 2013 speech were part of a trove of documents from the hacked email account of the Clinton campaign chairman released by anti-secrecy website WikiLeaks earlier this month.

It was not possible to confirm the authenticity of the leaked email, which contained a number of excerpts from Clinton's private speeches — including several focusing on China and Japan. The former secretary of state's campaign has neither confirmed nor denied the authenticity of hacked emails.