A third round of Federal Reserve bond purchases should only be done if the U.S. economy deteriorates, and the United States is not in that situation now, a top Fed official said on Friday.

The U.S. economy is looking brighter, with good data in the labor market and elsewhere, so it is a "natural time" for the central bank to pause and await more data, St. Louis Federal Reserve President James Bullard said on CNBC television.