Toward 1350 GMT, yields on three-month Treasury bonds fell to 2.455 percent, below those for 10-year bonds, which were at 2.447 percent.

Traditionally, the more investor dollars bet on longer-term returns, the steeper the curve. An inverted curve is a market anomaly and something that has occurred several quarters before all economic recessions in recent decades.

The spread between the two-year and 10-year bonds, another closely watched indicator, has yet to flip.

But research from the San Francisco Federal Reserve Bank recently claimed that the three-month, 10-year spread is the more meaningful indicator.