Why has US-China trade war restarted and how have markets reacted?

Trump has threatened 100% tariffs after Beijing's fresh curbs on rare earths, a month before deadline to agree a deal

With nearly a month to go before the deadline for the US and China to reach a deal in their trade war, goodwill between the two countries appears to have been swept off the table in recent days. China announced that it was once again restricting the export of critical minerals, prompting the US president, Donald Trump, to announce tariffs of 100% on US-bound Chinese exports, scuppering - at least for now - hopes that global economic turmoil could be averted.