President Donald Trump threatened to hike tariffs on South Korean goods, and the dollar sank to the lowest in nearly four years on mounting speculation the US may help Japan to support the yen, making precious metals cheaper for most buyers. Gold’s dramatic rally – the metal has more than doubled over the last two years – drives home bullion’s historic role as a gauge of fear in markets. The US leader’s warning to South Korea follows a threat to Canada over the weekend to impose 100% tariffs if Ottawa makes a trade deal with China.