Chinese leader Xi Jinping has pledged to lower car tariffs, improve intellectual property protection and open up the Chinese economy, addressing United States complaints in an escalating trade dispute. Xi made his remarks on Tuesday at the Boao economic forum on the southern island of Hainan. He did not mention US President Donald Trump directly. "China's door of opening up will not be closed and will only open wider," Xi said in his first public speech since the outbreak of trade tensions between China and the US. Also on Tuesday, it emerged that China filed a complaint against the US at the World Trade Organization (WTO) over steel and aluminium products tariffs imposed by Washington.