The operations are part of a continuation of the Fed's "Operation Twist" stimulus effort, which extends the maturity of the US central bank's holdings of Treasury debt in a bid to lower mortgage rates and other long-term borrowing costs. The program is scheduled to finish at the end of December.

An additional sixth sale has been tentatively scheduled for the afternoon of Dec. 27 to ensure the total sale and redemption amount is met, the New York Fed said, adding the schedule will be updated on Dec. 20 with details on whether the Dec. 27 sale is necessary.

For full details see

http://www.newyorkfed.org/markets/tot_operation_schedule.html

The Fed will also redeem about $400 million in Treasury securities in December, the New York Fed said.