U.S. President Donald Trump risks hurting investor sentiment if he removes Jerome Powell as chair of the Federal Reserve, according to a former American central bank governor.

Investors have in recent months become increasingly nervous as trade tensions between the U.S. and China rise. Conflict between the two major powers have threatened to derail economic growth even further at a time when the global economy has shown signs of slowing down.

"To fire a Federal Reserve governor or chairman would be a very unprecedented move, it would result in turmoil in the financial markets, it would be something that you really don't want to do because you don't need an absolute increase in uncertainty which this would bring about," Robert Heller, a member of the Fed's Board of Governors from 1986 to 1989, told CNBC's "Street Signs" on Thursday.

Heller's comment came as Bloomberg, citing people familiar with the matter, reported on Wednesday that Trump said he believes he has the authority to demote Powell.

The president had publicly blamed the Fed's interest rates hikes for holding back U.S. economic growth. He considered demoting Powell in February, Bloomberg reported on Tuesday. After the Fed announced its monetary policy decision on Wednesday, Powell said he intends to serve his full four-year term.

"The law is clear that I have a four-year term," the central bank chief emphasized.