Four former heads of the Federal Reserve have issued a public letter in the Wall Street Journal on Monday, warning that the U.S. central bank must be independent, instead of being swayed by a small group of politicians. 

In the public rebuke op-ed published by the WSJ, Paul Volcker, Alan Greenspan, Ben Bernanke and Janet Yellen wrote that the Federal Reserve must be able to make decisions "based on the best interests of the nation, not the interests of a small group of politicians," or it will disrupt financial market and damage the U.S. economy. 

The Fed's former heads didn't mention U.S. President Donald Trump, yet it's no secret that Trump has repeatedly criticized Fed's dovish policies, and called for the Fed to cut interest rates several times on his Twitter. 

Act in the best interest of the economy

"We are united in the conviction that the Fed and its chair must be permitted to act independently and in the best interests of the economy, free of short-term political pressures and, in particular, without the threat of removal or demotion of Fed leaders for political reasons," the former Fed chiefs wrote.

"Collectively, we served our nation across nearly 40 years and were appointed and reappointed by six presidents, both Republican and Democratic… In retrospect, not all our choices were perfect. But we believe those decisions were better for being the product of nonpartisan, nonpolitical assessments... rather than being motivated by short-term political advantage," the four former Fed leaders wrote.

Cut interest rates for first time since 2008 crisis

Last week, the Federal Reserve cut interest rates by 25 basis points to a range of two percent to 2.25 percent after its two-day policy meeting. The widely expected quarter-point decrease was the Fed's first since 2008.

Some investors suggested that the Fed may cut interest rate several times during the year. But the Fed chief Jerome Powell said the move was policy adjustment, not the beginning of a long series of rate cuts.

Trump earlier tweeted: "The Fed has made all of the wrong moves. A small rate cut is not enough."

Powell said that the rate cut is to guard against downside risk and trade policy uncertainty, which can help offset the adverse effects of these factors on the U.S. economy, and push the U.S. inflation back to two-percent target.

'He's my pick, and I disagree with him entirely'

"He's my pick, and I disagree with him entirely," Trump's said while commenting on Powell.

As recently as December, Trump discussed firing Powell after the four interest rate hikes in 2018, and widespread losses in the stock market.

Powell was nominated to the Fed Chair by President Trump, but was repeatedly accused by the president for not doing enough to help his administration to boost economic growth.

"I have the right to demote him. I have the right to fire him," Trump said in an interview in June, adding that the Fed went too far in raising rates and trimming its bond holdings.

But Powell said the law is clear, and he fully intends to serve the four-year term. Powell said he wouldn't step down from his job if Trump attempted to fire him.