Yields on the longest-dated US government debt have surged back to levels last seen before Treasury Secretary Scott Bessent rattled markets last month by unveiling an expanded bond buyback program aimed at curbing rising borrowing costs. That strategy provided temporary relief, but a global bond selloff has since pushed US government borrowing costs higher once again.

By Tuesday, the 30-year Treasury yield had climbed to 5.27%, matching the same level it sat at just before Bessent's August 19 announcement. Meanwhile, the 10-year yield—a key benchmark for borrowing costs across the economy—has risen more than 10 basis points above its pre-announcement level, hovering around 4.8%. These moves send a clear signal from the world's largest bond market: temporary adjustments to the Treasury's buyback program are not enough to placate investors concerned about surging government debt and persistently high inflation.

"Even when Treasury yields pull back noticeably, they just can't hold," said Mark Cabana, head of US rates strategy at Bank of America. "Investors are demanding the highest possible risk premium to lock their money up for such a long duration." The benchmark 10-year yield climbed to 4.80%, its highest level since January 2025, just before President Donald Trump returned to the White House.

The 2-year Treasury yield, which is most sensitive to the Federal Reserve's near-term policy expectations, rose 6 basis points to 4.40% on Tuesday. Traders are now pricing in roughly a 70% chance that the Fed will raise interest rates at its meeting this month—a move that would mark the first hike since 2023. The 30-year yield, meanwhile, remains slightly below the 19-year high it touched before the Treasury's intervention.