The recent spike in US long-term Treasury yields has wiped out the effects of Treasury Secretary Scott Bessent's unexpected expansion of the buyback program last month, sending borrowing costs back to previous highs. The strategy initially appeared to curb the yield surge, but a renewed global sell-off has quickly pushed government debt costs higher again.

As of Tuesday, the 30-year Treasury yield hit 5.27%, exactly matching the level seen on August 19th before Bessent's announcement. Meanwhile, the 10-year yield, a key benchmark for various lending rates, has climbed more than 10 basis points from that point, hovering near 4.8%. Market movements send a clear signal: a one-off buyback adjustment is far from sufficient to address investor concerns over the soaring federal debt and persistently high inflation.

Mark Cabana, head of US rates strategy at Bank of America, noted that the rates market has been unable to hold any significant downside moves, as investors demand higher risk compensation to extend duration. The benchmark 10-year Treasury yield has risen to 4.80%, its highest level since January 2025, just before Trump's return to the White House. The 2-year yield, most sensitive to near-term Fed policy expectations, rose 6 basis points to 4.40% on Tuesday, with traders pricing in roughly a 70% chance that the Fed will initiate its first rate hike since 2023 at this month's meeting. The 30-year yield remains slightly below the 19-year high set before the Treasury intervention.

This pressure is spreading to long-term bonds globally, driven by the same oil-price-induced inflation shock and government spending concerns. Germany's 30-year yield hit its highest level since 2011, while the UK's same-maturity yield reached levels not seen since 1998. Australia's 30-year yield set a record high since data collection began in 2016, and the Bloomberg Global Sovereign Bond Index yield has also climbed to near two-decade highs.

"Buybacks cannot replace the fundamental work needed to structurally lower yields. Developed markets are entering a cycle of higher real rates, underpinned by stronger nominal growth, rising neutral rates, large-scale AI-related investment and productivity gains, as well as increased private sector issuance competing with Treasuries. This creates powerful headwinds for the buyback policy," a macro strategist noted.

Of course, this does not mean the Treasury's efforts have been entirely ineffective. The expanded buyback program won't officially launch until September 9th, and the final purchase size remains uncertain. The Treasury announcement only stated that operations would be "at least doubled" without specifying an exact amount. Several market indicators also suggest that without this intervention, US long-term borrowing costs could have been even higher. For instance, since the announcement, Treasuries have outperformed same-maturity interest rate swaps, and long-end yields have risen less than the short end during this period.

Bessent himself remains unfazed by recent market movements. He previously characterized the move as an attempt to guide a market that was running disordered and detached from fundamentals back to normal. In a CNBC interview this week, he said, "I don't see a problem. The market is the market." However, the yield rebound highlights the challenge Bessent faces, given his claims that the Treasury possesses a "vast toolbox" to suppress rates. Lowering yields, and thereby reducing mortgage and other lending rates, has been a stated goal of the Trump administration since early last year. But investors point out that the government's massive spending, tax cuts, tariffs, and conflict with Iran have had the opposite effect.

Dan Morehead, founder and managing partner of Pantera Capital Management, told Bloomberg Television, "Bluffing only works when nobody at the table knows you're bluffing. I think this time it backfired."