The dollar and US stocks have fallen sharply after Donald Trump called the US Federal Reserve chairman a "major loser".
The US president took to social media to attack Jerome Powell, urging him to slash interest rates "pre-emptively" to boost the economy.
Trump has been critical of the US central bank boss, claiming he has been too slow to respond to economic developments.
His post online, the BBC reports, read: "There can be a SLOWING of the economy unless Mr. Too Late, a major loser, lowers interest rates, NOW."
Trump's imposition of sweeping trade tariffs across the globe have already caused significant market turbulence, and the continuing fallout between the president and Powell has added to the turmoil.
The S&P 500, tracking 500 of the largest US companies, fell around 2.4% on Monday, taking its total drop since the start of the year to approximately 12%.
The Dow Jones Industrial Average also fell 2.5%, about 10% for the year, while the Nasdaq lost more than 2.5% and is down roughly 18% in 2025.
And the dollar also dropped to its lowest level against the euro since 2022, with the pound climbing to a seven-month high against the dollar.
Sterling climbed 0.3% to $1.342, The Telegraph reports.