Facing unrelenting losses in the bond market, Treasury Secretary Scott Bessent -America's self-proclaimed "top bond salesman"-stepped in last month to try and cushion the pain. Now, Treasury investors will see just how far he's willing to go to support them this week.

Background: Bessent's Treasury, on Aug. 19, unexpectedly announced it will purchase significantly more bonds from investors than previously communicated. The announcement appeared to go against Treasury's practice of being regular and predictable-it also framed Bessent as a debt manager who's willing to take unprecedented actions to cull losses. Thirty-year yields, at the time of the announcement, were trading near 19-year highs. When bond prices fall, yields rise.

Bessent's resolve to help the bond market is about to put to test. On Wednesday, 11 a.m. Eastern to be precise, Treasury will share the maximum amount of government bonds-maturing in 10 to 20 years-it's planning to snap up. On Sept. 10, it'll reveal the exact amount actually purchased as part of the buyback program operating since May 2024.

Previously, the Treasury had said it will buy back at least $4 billion each time it goes to buy long-duration Treasuries from the market, through Nov. 4-up from $2 billion. But the department retains discretion to buy more. And the market fully believes Bessent is going to overshoot the communicated target.

"If all they buy on Sept 9 is $4 billion, I would expect the market to be disappointed," Will Denyer, lead U.S. economist at Gavekal Research, wrote to Barron's. "There is a pretty good chance he buys significantly more than that, especially with yields still pushing higher."

How will that "disappointment" play out? By a further sell-off in the bond market. Long-dated bonds, as measured by the iShares 20+ Year Treasury Bond exchange-traded fund, have been hammered this summer. The ETF is down 5% since late June on a total return basis and 6% on a price return basis.

"I think the market sniffed out the issue, which is fairly trivial buybacks are not going to solve the problem," Loren Moran, bond portfolio manager at Wellington Management told Barron's. "There's more risks [if] they don't surprise to the upside."

The problem here is that Bessent is targeting the the flow of debt, but not the stock, or the amount of debt. Treasury issues over $230 billion in 10-, 20-, and 30-year bonds quarterly and buying some back trims the flow. But at $40 trillion and counting, the quantity of debt existing remains large. Barclays' estimates roughly $4 trillion of debt maturing in over 10-years is outstanding. Investors decide at what price they buy the outstanding debt and Treasury buybacks don't change that.

That's why an announcement for a modest $2 billion increase in buyback had effectively no impact. Yield on a 30-year bond ended the latest week at 5.246%, nearly matching the 5.284% seen prior to the buyback announcement.

Bessent also hasn't been shy about his hands-on approach with the Treasury. He said in his latest media interviews that the buyback push was designed to soothe the headline-driven volatility during a quiet trading window. That was in contrast to the Treasury's announcement that cited strong demand from traders as a reason to increase the buybacks suddenly.

Now Bessent is in the spotlight again this week and he has got to deliver.

RBC Rates Strategy is expecting $6 billion in buybacks but that "would largely be a status quo development," Izaac Brook, rates strategist at RBC Capital Markets tells Barron's. Anything "larger than $6 billion would be bullish," he said.