"The drop from 7 to 6.7 percent I think reinforces the need to add some qualitative interpretation to the threshold or to find a different way to communicate," Atlanta Fed President Dennis Lockhart told reporters on Monday.

The Fed has said it will keep rates near zero well past the time unemployment falls below 6.5 percent, especially if inflation remains below its 2 percent target.

(Reporting by Jonathan Spicer; Editing by Chizu Nomiyama)