BEIJING — Less than a week into U.S. President Joe Biden's new administration, Chinese President Xi Jinping struck a confident tone Monday when he called for world leaders to cooperate more with China.Xi's keynote speech at the World Economic Forum's virtual Davos Agenda event comes as the world waits for a new phase in U.S.-China relations under Biden, following former President Donald Trump's single-handed approach.China is on track to surpass the U.S. as the world's largest economy in a few years and has gradually increased its global presence.Countries will fail if they operate alone, Xi said Monday. He did not mention the U.S. or specific countries, but named the United Nations in a call for international cooperation.