China vowed not to bow to "blackmail" from the United States as a global trade war ignited by US President Donald Trump's sweeping tariffs showed little sign of abating on Tuesday, even as battered stock markets steadied.

The International Monetary Fund (IMF) and ratings agency Moody's ramped up pressure on Britain to reverse a new economic strategy that was roiling financial markets for a fourth day on Wednesday and has sparked growing alarm about the UK housing market.