In the middle of international trade disputes, Trump in an interview with Reuters also accused China and Europe of manipulating their respective currencies.

American presidents have rarely criticised the Fed in recent decades because its independence has been seen as important for economic stability. Trump has departed from this past practice and said he would not shy from future criticism should the Fed keep lifting rates.

The president spooked investors in July when he criticised the US central bank's over tightening monetary policy. On Monday he said the Fed should be more accommodating on interest rates.

"I'm not thrilled with his raising of interest rates, no. I'm not thrilled," Trump said, referring to Powell. Trump nominated Powell last year to replace former Fed Chair Janet Yellen.

US stock prices dipped after Trump's comments to Reuters and the US dollar edged down against a basket of currencies.

Trump, who criticised the Fed when he was a candidate, said other countries benefited from their central banks' moves during tough trade talks, but the United States was not getting support from the Fed.

"We're negotiating very powerfully and strongly with other nations. We're going to win. But during this period of time I should be given some help by the Fed. The other countries are accommodated," Trump said.

The Fed has raised interest rates twice this year and is expected to do so again next month with consumer price inflation rising to 2.9 per cent in July, its highest level in six years, and unemployment at 3.9 per cent, the lowest level in about 20 years.

After leaving its policy interest rates at historic lows for about six years after the 2008 global financial crisis, the Fed began slowly raising rates again in late 2015.

A Fed spokesman declined to comment on Trump's remarks on Monday.

Powell last month said in an interview that the Fed has a "long tradition" of independence from political concerns, and that no one in the Trump administration had said anything to him that gave him concerns on that front.

"We're going to do our business in a way that's strictly nonpolitical, without taking political issues into consideration, and that carries out the mandate Congress has given us," he said.

Financial market analysts doubt current Fed policy makers are likely to be cowed by Trump's outbursts over their policy choices.

Still, it might affect candidates for openings on the bank's seven-member board, said Guy LeBas, fixed income strategist at Janney Montgomery Scott in Philadelphia. Currently only three seats are filled.

"I doubt these comments move the needle for Powell and his colleagues, but it certainly sends a strong signal to those candidates interested in vying for one of the Fed Board's many open seats: favour easy money policy or find another job," LeBas said.

Australian Associated Press