The minutes of the Federal Reserve's latest monetary policy meeting showed there was some discussion about weighting the central bank's purchases of Treasury securities toward longer maturities.

A statement released after the mid-December meeting revealed the Fed plans to continue purchasing bonds at a rate of at least $120 billion per month until "substantial further progress" has been made toward its policy goals.

The minutes revealed the meeting included conversations about how the Fed would determine whether "substantial further progress" had been made.

The Fed said participants commented that the judgment would be broad, qualitative, and not based on specific numerical criteria or thresholds.

Some participants drew attention to the importance of the Fed clearly communicating its assessment of actual and expected progress toward its longer-run goals well in advance of the time when it could be judged substantial enough to warrant a change in the pace of purchases.

Regarding the pace and composition of the asset purchases, the Fed said all participants agreed to continue the purchases at the current pace and nearly all favored the current composition.