Plosser, who backed the Fed's decision last week to modestly trim the purchases, has long been in the minority of policymakers opposed to the 17-month old program of buying Treasurys and mortgage bonds to support the U.S. recovery, which has been slow in recent years but picked up toward the end of 2013.
While he is unlikely to sway new Chair Janet Yellen and the Fed's others core decision-makers, his speech suggests he is ready to dissent if the central bank continues trimming the program by only $10-billion monthly increments at future meetings, as most economists expect.
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According to prepared remarks, Plosser argued that labor market conditions are "improving rapidly" and inflation, while low at just over 1 percent, "has stabilized" and is expected to strengthen.
"The longer we continue purchases in such an environment, the more likely we will fall behind the curve in reducing the extraordinary degree of monetary policy accommodation," Plosser was to tell an economic seminar in Rochester.
"With the economy awash in reserves, the costs of such a misfire could be considerably higher than usual, fomenting higher inflation and perhaps financial instability."
Besides the asset purchases, which are now running at $65 billion per month, the Fed has promised to keep interest rates near zero until well past the time unemployment falls below a 6.5-percent threshold, especially if inflation remains low.
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Though the Fed has stressed that the two easy-money policies—bond-buying and low rates—are separate, Plosser said "communications problems" loom if the economy continues to gather strength.
"My preference is to scale back our purchase program at a faster pace to reflect the strengthening economy," he said. "I would like to see purchases concluded before the unemployment rate reaches the threshold, which is likely during the first half of the year."
Plosser noted that, so far, turmoil in the emerging markets is not a big risk to the U.S. economy.
—By Reuters. CNBC contributed to this report.