The debate is on as to whether the Federal Reserve will start increasing interest rates in September or December. The former would definitely be a mistake, says Cullen Roche, founder of Orcam Financial Group.

Indeed, "I think that would be nuts," he writes on MarketWatch.

And why is that? "We are still muddling along following the financial crisis," Roche states. "Yes, the crisis is in the rear view mirror, but the effects still linger."

The economy grew a mediocre 2.3 percent in the second quarter, and the Atlanta Fed's forecasting model puts third-quarter growth at only 1.3 percent.

In addition, growing concerns about a slowdown in China shook markets around the world on Friday, driving the U.S. stock market to its biggest drop in nearly four years.

Roche also cites weakness in housing investment, wages and commodity prices. Average hourly earnings rose only 2.1 percent in the year through July, and major commodity indices have plunged to 13-year lows, with oil continuing its swoon. Turmoil overseas also argues for a cautious Fed, Roche says.

"Does this look like an inflationary environment that warrants higher rates?" The Fed has kept short-term rates at a record low near zero since December 2008.

Narayana Kocherlakota, president of the Minneapolis Fed, agrees with Roche.

"Many observers have called for the [Fed] to tighten monetary policy by raising interest rates in the near term," he writes in The Wall Street Journal. "But such a course would create profound economic risks for the U.S. economy."

Inflation stands well below the Fed's 2 percent target, Kocherlakota notes. The central bank's favored inflation gauge showed prices climbed only 0.3 percent in the 12 months through June.

"The outlook is for more of the same," Kocherlakota says. "The U.S. inflation outlook thus provides no justification for policy tightening at this juncture."

The Fed should actually ease policy rather than tighten it, he maintains. And how should the Fed ease? "For example, buying more long-term assets or by reducing the interest rate that it pays on excess reserves held by banks," he suggests.

Related Stories:

• Yale's Shiller: 'Even Biggger' Plunge Can Follow Market Bloodbath
• El-Erian: China, Fed Face Big Task in Calming Investor Panic