The criticism has tended to fall along three lines. Some have accused the Fed of deliberately weakening the dollar to make American exports more competitive. Others fear the Fed’s decision could ignite inflation down the road. Still others say the policy will be ineffective absent additional fiscal stimulus.

Fed officials were clearly unsettled by an opinion piece by Mr. Greenspan in The Financial Times on Thursday, at the start of meetings of the Group of 20 nations in Seoul, South Korea. Mr. Greenspan said the United States was “pursuing a policy of currency weakening” and increasing the risks of trade protectionism.

In an open letter to Ben S. Bernanke, the Fed chairman, on Monday, a group of conservative economists, writers and investors urged that the Fed’s action “be reconsidered and discontinued,” arguing that the bond purchases “risk currency debasement and inflation.” The group included Michael J. Boskin, a former chairman of the White House Council of Economic Advisers; the historian Niall Ferguson; Douglas Holtz-Eakin, a former director of the Congressional Budget Office; and the economist John B. Taylor, one of Mr. Bernanke’s most prominent critics.

Mr. Dudley did not single out any critic, but suggested that the criticisms were unfounded.

“There is no long-term conflict between what the U.S. is trying to accomplish and what other countries are trying to accomplish,” Mr. Dudley said, echoing statements by President Obama and Treasury Secretary Timothy F. Geithner. “A strong economic recovery in the U.S. is in the interests of the global economy.”

While Mr. Dudley said the effect on the dollar was not a consideration, he acknowledged that when interest rates adjust, “oftentimes there will be consequences for the dollar.” He added, “We have seen some dollar weakness in this period, but it doesn’t seem to be unusual, given the changes that we’ve seen in interest rates in the U.S. compared to interest rates abroad.”

Mr. Dudley rejected the idea that the Fed might be setting the stage for uncontrollable inflation in years to come. He said the Fed had tools for draining the bank reserves sitting on its balance sheet.

“We are very, very confident that those tools will be completely effective at keeping inflation in check,” he said. “We are completely willing to use those tools, when the time comes, to prevent an inflation problem. Higher inflation is not a way out. It is not a solution.”