"If the conditions are right, then I would anticipate we'll take advantage of long-term borrowing and execute on that," Mnuchin said Wednesday in a Bloomberg interview in Washington. He said officials held a meeting earlier in the day to review the possibility.

The concept of issuing 50- or 100-year bonds dates back to at least 2009 and has recently gained traction within Treasury. For the Trump administration, issuing extremely long-term debt would limit the cost to taxpayers of plugging a budget deficit that's headed to $1 trillion annually. Pension funds would enjoy a few extra points of returns amid falling yields.

Mnuchin said his renewed interest in long bonds was unrelated to the drop in yields on shorter-term U.S. debt. The yield on 30-year Treasuries slid below 2% for the first time earlier this month, and they continued their decline to a new record 1.90% on Wednesday.