Ron Insana, a CNBC and MSNBC contributor and the author of four books on Wall Street, is urging the Federal Reserve to stop creating confusion about its rate strategy, which in turn is unnerving investors and the stock market.

“The Federal Reserve is creating a negative-feedback loop with its mixed messages on interest rates — and it's messing with the markets,” he wrote on CNBC.com.

“If the Fed continues to convey confusing messages about the timing of normalization, in an abnormal world, it will only serve to exacerbate the very trends it is hoping will abate,” he wrote.

The Federal Open Market Committee decided last week to keep its benchmark rate near zero and released a statement that put an unexpected emphasis on low inflation and an uncertain outlook for global growth.

While Fed Chair Janet Yellen has said the central bank is likely to raise rates in 2015 if the economy expands as expected, she said last week that policy makers needed more time to assess the impact of the slowdown in China and other emerging economies on U.S. growth and inflation.

“If slowing global growth and market turbulence was a reason to pause, how likely was it, then, that all of that would be resolved by October?” he asked.

“Since Chair Yellen spoke, a number of Fed officials have spoken, reiterating that a rate hike in 2015 remains likely. This is cognitive dissonance at its worst. Investors are now simultaneously worried about incompatible outcomes,” he wrote.

“If growth is weak, and inflation continues to fall, the Fed should NOT, and would NOT, raise rates. If this global problem is truly transitory (a word most Fed officials need to look up in the dictionary), then a rate hike should have already occurred,” he wrote.

“If the world is not normal, why normalize policy at all? The world affects the U.S. As we have seen in innumerable instances in the past, global instability has altered the course of domestic monetary policy for decades.”

Meanwhile, the Fed likely will pull the trigger and hike interest rates in December after taking a pass last week, according to economists polled by Reuters who assigned a 60 percent probability of it happening.

"The window for a rate hike this year has narrowed. While December remains in play, a rate hike this year is not a foregone conclusion," Ellen Zentner, chief U.S. economist at Morgan Stanley wrote in a note.

(Newsmax wires contributed to this story).

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