Many Detect End of Line For Stimulus By the Fed WASHINGTON - The beginning of the end probably will not come on Wednesday, but it is coming soon. The Federal Reserve has made clear that its bond-buying campaign will not continue at the present pace for much longer. Almost from the outset of the campaign last fall, some Fed officials have expressed doubts about the economic benefits and concern about the consequences of a deepening commitment to a relatively untested approach to monetary policy. So far, the realities of high unemployment and slow growth have outweighed those misgivings, and the Fed has continued to expand, by $85 billion a month, its holdings of Treasury securities and mortgage-backed securities. Analysts generally expect the Fed's policy-making committee, which meets on Tuesday and Wednesday, to once again defer any changes in the program, although a spate of stronger economic news has increased the odds of a policy shift. Even among Fed officials who support the bond-buying program, however, there is general agreement that the Fed should taper off on its bond buying and focus on stimulating the economy by other means. It's just a matter of timing. The broad outlines of the shift also are clear. The Fed intends to lean even more heavily on "forward guidance," trying to hold down borrowing costs for businesses and consumers by declaring its intent to keep short-term interest rates near zero. "We have sought to ease financial conditions further and provide additional impetus to the recovery," Ben S. Bernanke, the Federal Reserve chairman, said Monday at a celebration of the Fed's 100th anniversary, "by communicating, both quantitatively about the likely future path of our policy rate and qualitatively about the likely evolution of our balance sheet." The event, a rare break from the Fed's general practice of avoiding public comment in the days before a policy meeting, was held as a matter of convenience because so many Fed officials were already planning to be in Washington this week. The actual anniversary is Dec. 23. Attendees included the former Fed chairmen Alan Greenspan and Paul A. Volcker, along with Janet L. Yellen, who is expected to be confirmed by the Senate this week to lead the Fed for the next four years. Fed officials say that the impending shift reflects the progress of the economic recovery, and that it could improve the effectiveness of forward guidance by focusing public attention on a single stimulus program. But there are plenty of skeptics. Stanley Fischer, the former governor of the Bank of Israel and leading candidate to be nominated by President Obama as the next vice chairman of the Fed, has suggested in recent public remarks that the power of forward guidance is constrained because the future is unpredictable, so investors will correctly discount the Fed's forecasts. Adam S. Posen, president of the Peterson Institute for International Economics, has advanced a similar critique, arguing that bond buying is a more effective form of stimulus than forward guidance, and that investors are more likely to take the Fed seriously when it acts, not just talks. Mr. Bernanke and his allies say that bond buying will soon have served its purpose. While academics have struggled to isolate the effects of the campaign, officials assert that it has helped to lower a wide range of borrowing costs, leading to increased sales of cars and other consumer goods, and contributing to a modest climb in job creation. Some Fed officials argue that these benefits have begun to diminish. Moreover, on a technical level, bond buying has stronger effects when financial markets are in disarray. "The bottom line is that diminishing returns will eventually affect any bond purchase strategy, whatever its design and initial effects," the International Monetary Fund concluded in an analysis published in April. Policy makers most likely need to either accept this diminishing impact or adopt new and more radical policy frameworks over time. But there is no consensus inside the Fed that the benefits of the bond buying, often referred to as "quantitative easing," are wearing off. "I don't buy this diminishing returns thing," James Bullard, president of the Federal Reserve Bank of St. Louis, said in an interview with Bloomberg Television last month. If you lowered the funds rate from 5 percent to 4 percent, and then you lowered it from 4 percent to 3 percent, you probably wouldn't say that the second hundred basis points was less effective than the first 100 basis points. And I don't think we should say that about the Q.E. program either. Officials are also not particularly afraid of inflation. While some Fed officials worry about the risk that buying bonds will lead to faster inflation, the Fed, if anything, is increasingly confronting the opposite problem. Several Fed officials in recent weeks have expressed puzzlement over why prices have been rising at an unusually sluggish pace. There is another technical issue. Lower federal deficits have reduced the issuance of government debt, so the Fed is buying a growing share. And as higher interest rates have reduced the demand for mortgage loans, the Fed is buying a larger share of government-backed mortgage bonds, too. The best argument for tapering sooner rather than later? Peter R. Fisher, senior director at the BlackRock Investment Institute, wrote in a recent analysis. The Fed is running out of stuff to buy. He estimated that if it maintained the current level of asset purchases, the Fed could soon be consuming all the new issuance of Treasuries and mortgage bonds. But the most important risk associated with bond buying is also the most fundamental. The point of the program is to encourage risk-taking by business executives and investors, but one of the Fed's main concerns is to avoid encouraging too much risk-taking. For now, there is a greater risk to worry about: that the economy could slip back toward recession if the Fed fails to do enough to encourage growth. As the economy shows signs of improving health, however, the Fed is reverting to its most basic fear: that it will do too much.