"Does it tell you people think the Fed will raise rates or does it tell you people don't want to put money to work ahead of the Fed? I think it's more of the latter," said Briggs. "I think some of the move you're seeing is buyers might be reluctant to step in ahead of the Fed and they think there might be better levels on Thursday."
Yet, the two-year note yield, the most reflective of Fed hiking, jumped to 0.8 percent for the first time in four years.
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"There's a lot of selling going on. The markets are very thin and either someone is unwinding positions or someone is making a little bet that the Fed is going to raise rates. We've seen a few large trades on the front end," said Justin Lederer, rate strategist at Cantor Fitzgerald.
Strategists also pinned the action, where there was a big move higher in stocks and selloff across the yield curve on asset allocation trades. The 10-year yield for instance, also moved higher to 2.27 percent.
"The market just felt heavy all day, and there was a lot of selling going in on the front end in the last few days. There were more sellers there today. If you think the Fed was going to go, you would expect the curve to flatten, but it's done anything but that," Lederer said.