SYDNEY, July 20, 2016 (Xinhua) -- U.S. Vice President Joe Biden (C) delivers a speech in Sydney, Australia, July 20, 2016. Australia is key to the core of the United States' Asia-Pacific pivot as each country has the other's back, visiting U.S. Vice President Joe Biden said as he ends his visit here on Wednesday. (Xinhua/Hongye Zhu)