Several Federal Reserve policy makers said the central bank should be ready to vary the pace of their $85 billion in monthly bond purchases amid a debate over the risks and benefits of further quantitative easing.

The officials "emphasized that the committee should be prepared to vary the pace of asset purchases, either in response to changes in the economic outlook or as its evaluation of the efficacy and costs of such purchases evolved," according to the minutes of the Federal Open Market Committee's Jan. 29-30 meeting released today in Washington.

The minutes showed policy makers were divided about the strategy behind Chairman Ben S. Bernanke's program of buying bonds until there is "substantial" improvement in a U.S. labor market burdened with 7.9 percent unemployment, with some saying an earlier end to purchases might be needed, and others warning against a premature withdrawal of stimulus.

At their December meeting, Fed officials debated the date for ending their bond purchases, with officials "approximately evenly divided" between those favoring mid-2013 and those favoring a later end, according to minutes from the meeting. Today's minutes didn't indicate a discussion of dates.

David Fuller's view I doubt that Fed officials know when QE will end. However, we all know that it will end and probably in the not too distant future. That prospect could easily roil markets.