Veteran economist Mohamed El-Erian predicts the Federal Reserve next month will be forced to hike interest rates for a fourth time in 2018 or risk being seen as politically coerced.

"If they don't [hike], the market is going to say the economy is much weaker than we anticipated and/or the Fed is much more open to political intervention," the chief economic advisor at Allianz told CNBC.

"It is very hard for the Fed right now to go back to three hikes," the Bloomberg Opinion columnist and Newsmax Finance Insider told CNBC.

Meanwhile, President Donald Trump has repeatedly criticised the Fed, recently describing the U.S. central bank as a “problem” as he called for lower interest rates.

“I’d like to see the Fed with a lower interest rate,” Trump told reporters last week in Washington. “We have much more of a Fed problem than we do with anyone else.”

The Fed held borrowing costs steady at its meeting earlier this month but investors expect it to raise rates in December, which would mark the fourth hike since Trump-appointed Jerome Powell became chairman in February.

The Fed rate decision next month will be "a real test as to whether the power of the Fed is indeed a different Fed or whether at the first sign of market volatility they flinch," El-Erian said.

"The Fed has put itself in a bit of a box and will have to go through with four hikes," he stressed.

For his part, Trump reportedly plans to keep Treasury Secretary Steven Mnuchin and Commerce Secretary Wilbur Ross amid speculation of a broader shakeup in the president’s Cabinet, three people familiar with his thinking told Bloomberg.

Trump has signaled that he plans to make changes at the most senior levels of his administration following midterm elections earlier this month in which his party lost control of the House of Representatives. But Mnuchin and Ross, who each have been the subject of reports that Trump is dissatisfied with them, will remain in their posts, the people said.

Trump said Friday he was “extremely happy and proud” of Mnuchin after The Wall Street Journal reported that he was displeased with the Treasury secretary in part for persuading him to select Jerome Powell to lead the Federal Reserve. Trump has openly criticized Powell and the Fed raising interest rates, saying the increases have jeopardized economic growth and a booming stock market.

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