The head of the US Federal Reserve faces no risk of losing his job, according to a White House official, and President Donald Trump has said he is happy with his Treasury Secretary.

Key points: The President has attacked the Fed, saying it's America's "only economic problem"

The President has attacked the Fed, saying it's America's "only economic problem" People speculated that Mr Trump planned to fire Federal Reserve chair Jerome Powell

People speculated that Mr Trump planned to fire Federal Reserve chair Jerome Powell Legal experts say it's not clear if the President can do so

Asked if Fed chair Jerome Powell's job was safe, White House economic adviser Kevin Hassett told reporters: "Yes, of course, 100 per cent."

In a press conference on Wednesday Mr Trump said he did have confidence in Treasury Secretary Steven Mnuchin, referring to him as a "very talented guy, very smart person".

"They're raising interest rates too fast. That's my opinion. I certainly have confidence. I think it will straighten," Mr Trump added.

Earlier on Tuesday, Mr Trump blasted the Fed, saying it was the US economy's "only problem", and investors have closely followed reports the president had privately discussed the possibility of firing Mr Powell.

The US central bank chief took his post early last February after being appointed by Mr Trump and has continued the path of gradual rate hikes started by his predecessor, Janet Yellen.

Mr Powell has come under fire for raising interest rates in line with his predecessor. ( AP: Susan Walsh )

Legal experts say it is not clear whether the President could in fact dismiss the chair.

US stocks edged up on Wednesday, with the S&P 500 up 0.2 per cent in late morning trading.

Stock prices have plunged in recent weeks on concerns about the economy.

The S&P 500 index was on pace for its biggest percentage decline in December since the Great Depression

Mr Hassett also said Mr Trump was happy with Treasury Secretary Steven Mnuchin, who in recent days has talked with top US bankers and convened a call with a working group of regulators who aim to keep financial markets running smoothly.

"I am highly confident that the president is very happy with Secretary Mnuchin," Mr Hassett told Fox Business Network.

AP