Traders reacted swiftly to US President Donald Trump’s declaration that he would push through with new tariffs on Mexico and Canada and an extra levy on China, dumping everything from stocks to bitcoin amid concern about the impact on global growth.

The selling was heaviest on Wall Street, with both the S&P 500 and the technology-heavy Nasdaq tumbling around 2 per cent overnight as the president dashed investor hopes that a last-minute deal could be reached. He also signed an order that doubles tariffs on China – Australia’s key trading partner – to 20 per cent.