The American stocks sell-off deepened on Monday after US President Donald Trump stepped up his calls for the Federal Reserve to cut interest rate on social media.

The president’s threats to remove the Fed Chair Jerome Powell have hit American assets broadly, weighing on longer-dated Treasuries and the dollar.

The S&P 500 sank 2.1 per cent and the dollar index weakened to a 15-month low as Wall Street reopened after the Easter holiday weekend. The benchmark 10-year fell with the yield close to 4.4 per cent.

As investors turned away from US securities, haven assets climbed. Gold jumped to another record, above US$3,400 an ounce, while the Swiss franc gained more than 1 per cent against the dollar.

The US president took to social media escalating his attack on the Fed chair, and insisted there was “virtually” no inflation, and it was time for “pre-emptive cuts”. The last reading of the Fed’s preferred inflation gauge remains above the central bank’s target, the next readout comes next week.

National Economic Council Director Kevin Hassett said on Friday that Trump was studying whether he is able to fire Powell.