Fissures are developing among policy makers at the Federal Reserve as they debate how and when to start raising the benchmark interest rate from its current level just above zero.

With Fed officials forecasting that unemployment will average 9.8 percent in 2010, nobody appears to be arguing that monetary policy should be tightened anytime soon. The central bank’s official mantra continues to be that the overnight federal funds rate will remain “exceptionally low” for “an extended period.”

But Fed officials have hinted at new disagreement in recent weeks. The arguments go beyond the traditional split between hawks, who worry that easy money will stoke inflation, and doves, who contend that unemployment is the top problem.

The more devilish debates are about how fast to act once the decision has been made, and how to carry it out. Beyond raising the overnight federal funds rate, the Fed also has to unwind $2 trillion in special programs that prop up paralyzed banks and credit markets.

Where Ben S. Bernanke, the Fed chairman, stands in the emerging argument is a question mark. At a conference held by the Fed on Thursday evening, he assured economists that the central bank had a detailed list of tools to reverse course but offered no new hint of when he planned to begin his exit strategy.

“When the economic outlook has improved sufficiently, we will be prepared to tighten the stance of monetary policy and eventually return our balance sheet to a more normal configuration,” Mr. Bernanke promised.

Any move to tighten monetary policy over the next year or so could set the stage for a clash between the Fed and the White House. The Obama administration has been outspoken in saying it does not want a quick end to stimulus policies, whether fiscal or monetary.

Policy makers are haunted by the results of previous miscalculations. Mr. Bernanke and others have warned that the central bank should not repeat its error in 1937, when it raised interest rates too early and helped extend the Depression for several years.

At the same time, officials at the Fed are acutely aware that it has been widely blamed for contributing to the housing bubble and the financial collapse by keeping the cost of borrowing too low for too long after the recession of 2001.

One hint of the discord came Tuesday, in a speech by Thomas M. Hoenig, president of the Federal Reserve Bank of Kansas City.

Though he stopped short of calling for immediate rate increases, Mr. Hoenig made it clear that he was getting impatient.

“My experience tells me that we will need to remove our very accommodative policy sooner rather than later,” he told an audience of business executives. “Even if we were to start immediately, much time would pass before incremental increases could be considered tight or even neutral policy.”