US stocks were tumbling on Monday after US President Donald Trump renewed his attacks on Federal Reserve Chair Jerome Powell, amplifying investors' concerns over the central bank's autonomy and its ability to keep inflation under control.

Trump nominated Powell for the head of the Federal Reserve in 2017, with Powell being nominated again by Joe Biden four years later. Powell's current term expires in 2026.

Last week, Trump called on Powell to cut interest rates to help stimulate the US economy. The US president then renewed his criticism on Monday, warning on social media of a slump unless "Mr. Too Late, a major loser, lowers interest rates."

Trump's outburst comes just days after a White House adviser signaled the Trump administration may look into ways of dismissing Powell.

Wall Street seems to be affected by the uncertainty, with the S&P 500 down 3.1% and the Dow Jones Industrial Average down 2.9% as of 1 p.m. Eastern time.

"Big Tech" stocks such as Elon Musk's Tesla saw some of the sharpest losses, dragging the Nasdaq composite down a market-leading 3.4%.

US dollars pressured by trade conflict

"Investors are worried about Fed independence," Jack Ablin, chief investment officer at Chicago-based Cresset Capital told the Reuters news agency. "If the president puts his own person in and lowers rates against a backdrop of rising inflation, we'll see a continuation of what we're experiencing now."

Meanwhile, the value of the US dollar also sank as uncertainty continued over Trump's tariffs on international imports and as yet unfulfilled promised of new trade deals, with foreign investors retreating further and further from US markets.

"Markets are showing disapproval of a lack of progress on trade negotiations," commented Jamie Cox, managing partner at Harris Financial Group in Richmond, Virginia. "In the absence of any firm commitments from any countries, markets take the 'fire first, ask questions later' [approach.]"

Edited by: Darko Janjevic