U.S. Treasury Secretary Steven Mnuchin leaves the G-20 Finance Ministers and Central Bank Governors' meeting at the IMF and World Bank's 2019 Annual Spring Meetings, in Washington, April 12, 2019. REUTERS/James Lawler DugganWASHINGTON (Reuters) - U.S. Treasury Secretary Steven Mnuchin said on Saturday a U.S.-China trade agreement would go “way beyond” previous efforts to open…