China promises to hit back over U.S. tariffs. Russia makes a petroleum play in the Middle East.
Russia's President Vladimir Putin (L) and Saudi Arabia's Crown Prince Mohammed bin Salman attend the G20 Leaders' Summit family photo in Buenos Aires, on November 30, 2018. - Global leaders gather in the Argentine capital for a two-day G20 summit beginning on Friday likely to be dominated by simmering international tensions over trade.