The U.S. Treasury raised the size of its planned buyback operation for Treasurys maturing in 10 to 20 years to $6 billion, triple the typical amount, but not enough to send yields lower.

The Treasury Department said last month that it would at least double buybacks of longer-term bonds to $4 billion. Yields rose following the release of that plan which suggested the increased size lacked enthusiasm for bond investors.

"Investors were looking for a much larger increase, with expectations centered around $7 billion to $8 billion...the continued climb in yields suggests the announcement fell short of those expectations," wrote Tracey Manzi, senior investment strategist at Raymond James.

The U.S. 10-year Treasury yield rose after the announcement to its highest intraday level since November 2023. However, as yields move inversely to bond prices, a strong 10-year Treasury note auction Wednesday afternoon relieved some pressure. The 10-year notes showed healthy demand from investors and were sold at their highest high yield since August 2007.

U.S. Treasury yields still ended the day marginally higher. The 10-year yield rose 0.030 percentage point to 4.836%, and 2-year yield rose 0.030 percentage point to 4.42%. The 30-year yield rose 0.021 percentage point to 5.285% Wednesday.

Treasury Secretary Scott Bessent said he doesn't believe Treasury yields reflect the underlying fundamentals following the announcement to increase buybacks on longer-end bonds last month. Separately, he said he does not believe he could change the equilibrium price of Treasurys.

Instead, Bessent said his job is to "speed things down" and make sure market participants know that things may not be on "a one-way trip."

Long-dated bond yields have risen globally amid concerns of mounting government debt, broader economic uncertainty and inflation from higher oil prices tied to the conflict in Iran. Brent oil crossed above $100-a-barrel for the first time since July on Wednesday after the latest round of strikes in the Middle East.

"The size of the intervention is rather small...and not likely to sway the inclination of investors to charge a higher risk premium and push yields higher as inflation continues to rise and concerns about the sustainability of the U.S. fiscal path mount," said Joe Brusuelas, chief economist at RSM.

In addition, Treasury straying away from its "regular and predictable" mantra could increase term premium in the long run, TD securities research strategist Molly Brooks said.

"We would not be surprised if we are not given much notice for long-end auction size decreases, which could be sooner than we initially anticipated before the buyback interventions were announced," Brooks wrote.

Yields were also higher in global markets. The 10-Year German Bund yield sat at 3.44%, above the previous 15-year high of 3.40%. Meanwhile the 10-Year U.K. Gilt Yield hovers around 5.27% from 5.21%. The WSJ dollar index is at 94.88 from 94.75 before the announcement.

The buyback operation is scheduled for Thursday.