As U.S. public debt surpassed the $40 trillion mark for the first time in history, long-term U.S. yields have reignited alarms over the cost of financing debt, in a potentially explosive cocktail that has raised red flags across financial markets, given that interest expenses have already become one of the fastest-growing budget items for the federal government. Markets remain on edge, awaiting the press conference by U.S. Treasury Secretary Scott Bessent, scheduled for today at 14:00 ET.

“Forty trillion dollars of debt does not in itself represent a macroeconomic tipping point,” says Christian Scherrmann, Chief U.S. Economist at DWS. “However, this figure clearly illustrates the extent to which U.S. fiscal policy has strayed from its historical path. In the long run, what will matter is not only the absolute level of debt, but also what proportion of economic output must be allocated to servicing it,” the expert warns.

In this context, the Federal Reserve maintains a restrictive stance, and the Treasury intervened last week to curb the rise in yields. According to analysts, the signal to markets is clear: money will no longer be as cheap or abundant as it was over the past decade. Put another way, the U.S. financial market is sending a signal that stock markets still seem unwilling to hear: the long-term cost of capital is taking on a life of its own.

An increasingly uncomfortable combination

While major equity indices continue to show resilience, the U.S. Treasury bond market—considered the benchmark for pricing virtually every financial asset in the world—is facing an increasingly uncomfortable mix of high inflation, massive government financing needs, strong capital demand for artificial intelligence and infrastructure, and doubts surrounding the future path of interest rates.

Tensions reached a notable milestone on August 19, when the Department of the Treasury announced that, starting in September, it will double the maximum size of its long-term bond buyback operations, raising them from $2 billion to at least $4 billion per operation for securities with maturities between 10 and 30 years.

The market reaction was immediate. The 30-year Treasury yield, which had topped 5.3% last week, fell about 10 basis points following the announcement, while equities and gold advanced. The move was significant because it came after long-term rates reached levels not seen since before the 2008 financial crisis. DWS notes, however, that “markets continue to offer few signs that investors are fundamentally questioning U.S. solvency,” given that demand at Treasury auctions remains solid, U.S. CDS spreads recently fell to 38 basis points, and even repeated sales by foreign investors—for example, during interventions on the Japanese yen—have failed so far to disrupt market balance. “Markets are signaling higher financing costs, but not a crisis of confidence,” the firm asserts.

However, money market specialists consulted by Funds Society point out that the most important message does not lie in the temporary drop in yields. It lies in why Washington felt the need to act.

It was not the Fed, but it was an intervention

The operation announced on August 19 was not a bond purchase by the Federal Reserve, nor was it a new quantitative easing (QE) program. It was a Treasury decision within its debt buyback program, originally designed to improve market liquidity.

The Treasury buys specific off-the-run bonds trading in the secondary market and, in doing so, helps free up balance sheet capacity for primary dealers and improve liquidity in specific segments of the curve.

Wednesday’s decision significantly increased the size of those operations for long maturities. The distinction is crucial: while the Fed controls monetary policy and financial system liquidity conditions, the Treasury manages the government’s financing needs. Nevertheless, both end up influencing the same variable: the price of money. And that is where one of the major market stories for the second half of 2026 emerges.

The Fed is not cutting rates

At its July 28–29 meeting, the U.S. Federal Reserve maintained the federal funds rate target range at 3.5% to 3.75%, a decision approved by a 9 to 3 vote.

The three dissenters—Beth Hammack, Neel Kashkari, and Lorie Logan—wanted to hike the rate by 25 basis points. In other words, a section of the Committee felt that the inflation problem justified additional tightening.

However, there is another particularly important element to understanding the bond market. The Fed continues to operate under an ample reserves regime. Its guidelines permit open market operations and, when necessary, purchases of Treasury bills and potentially other Treasuries with maturities of up to three years to maintain an ample level of bank reserves.

This means that the Federal Reserve is not engaging in QE in the traditional sense, as experts explain to Funds Society, but nor is it allowing bank liquidity to contract in a disorderly manner—a distinction that is highly relevant. Last week’s intervention should be understood more as market “plumbing” than a radical shift in monetary policy. But even that “plumbing” is acquiring enormous importance.

In this sense, the current strategy can be understood as a balance between two objectives. On one hand, the Fed wants to prevent bank reserves from falling too low and causing friction in the money market.

On the other hand, it does not want to return to the massive balance sheet expansion used during the pandemic and other crisis episodes. The Fed has indicated that it can use purchases of Treasury bills and, if necessary, other short-term securities to ensure that the system maintains sufficient reserves.

Furthermore, it maintains standing repo and reverse repo operations. Repo operations allow liquidity to be provided against high-quality collateral, while reverse repos temporarily absorb liquidity. The New York Fed explains that these operations form part of the mechanisms used to keep the federal funds rate within the range established by the FOMC.

Therefore, it would be incorrect to interpret any Fed liquidity operation as an automatic return to monetary expansion. In reality, the Fed is trying to manage liquidity without necessarily expanding its balance sheet aggressively again.

The problem is at the long end of the curve

According to analysts, this is the section that should concern investors the most. The Fed directly controls short-term rates, but it does not set the 10-, 20-, or 30-year Treasury yield.

Those rates depend on expectations for inflation, growth, fiscal deficit, bond supply, international demand, and the term premium. And that is precisely where pressures are emerging.

The 30-year Treasury reached over 5.3% last week, as the market faces a massive supply of U.S. public debt. At the same time, U.S. inflation remains above the Fed’s 2% target. The July minutes note that inflation remains elevated and that energy-related price increases are complicating the outlook.

The result is a difficult equation: more debt + higher issuance + above-target inflation + strong capital demand for AI and infrastructure = upward pressure on long-term rates.

The market is starting to demand a premium

For much of the past decade, investors grew accustomed to a world of ultra-low rates and abundant liquidity. That environment allowed equity, real estate, and private asset valuations to expand significantly.

Now the landscape is changing. An investor purchasing a 10- or 30-year Treasury is not only evaluating whether the Fed will cut or raise rates at its next meeting. They are also asking how much risk is involved in lending money to the U.S. government over decades.

That question increases the so-called term premium—that is, the additional yield investors demand to hold long-term debt given uncertainty surrounding inflation, growth, deficits, and economic policy.

And if that premium continues to rise, the Fed could lower short-term rates and still find that the rates that truly matter for much of the economy remain high. That is why the Treasury’s move is so important.

The Treasury’s announcement has a relatively small immediate effect compared to the overall size of the Treasury market, which stands at around $31 trillion. But its importance does not lie solely in the $4 billion per operation; in fact, that figure is also modest—what is truly important is the signal.

In practice, the powerful U.S. Treasury is telling the market that it is not indifferent to excessive turbulence at the long end of the curve.

“Policy makers do not have to be passive observers. When pressure emerged at the long end of the curve, the Treasury showed it has tools and is willing to use them,” commented Brian Levitt, Chief Global Market Strategist and Head of Strategy & Insights at Invesco. According to Levitt, the Treasury’s announcement reinforces something he has long believed: “The U.S. government is unlikely to sit idly by and allow a disorderly debt crisis to unfold if it has mechanisms to help address it.”

Paradoxically, the U.S. administration needs to keep the cost of financing its massive debt under control, while at the same time the Fed needs to maintain a sufficiently restrictive stance to combat inflation. There are signs that the problem may grow: according to a note published by DWS on Friday, August 21, if current borrowing trends persist, total U.S. Treasury debt could reach $50 trillion by 2029.

The Treasury wants to prevent long-term rates from spiking, whereas the Fed does not want to give the impression that it is bailing out the bond market. These are objectives that may align at times, but they are not exactly the same.

The real risk

The real risk is that equities could continue rising while the bond market deteriorates for a period of time.

However, that divergence cannot widen indefinitely because a higher long-term Treasury rate means, among other things: higher financing costs for corporations; higher mortgage rates; higher borrowing costs for governments; lower valuations for growth equities; higher cost of capital for infrastructure projects; pressure on private equity; higher return hurdles for private credit; and a higher discount rate for virtually all financial assets.

That is why the behavior of the Treasury is particularly relevant for investment funds, asset managers, wealth management, and family offices. It is not simply a matter of deciding whether to buy or sell bonds. It is a matter of determining what price every financial asset should carry in a world where long-term Treasuries are once again demanding significantly higher yields.

There is also a variable that sets this cycle apart. The U.S. economy is entering a phase of massive investments in data centers, semiconductors, energy, power grids, and technology tied to artificial intelligence, meaning the government is not the only major seeker of capital.

This competition can help keep financing costs elevated even if the Fed eventually begins cutting short-term rates; the problem, therefore, may not be purely monetary—it may be structural.

What does it mean for investors?

For portfolio managers, the scenario forces a review of a premise that dominated much of the past decade: that a drop in Fed rates would necessarily trigger a broad-based bond rally.

Today, that premise might not hold true. If short rates fall but long rates remain elevated due to deficits, inflation, debt supply, and capital demand, the yield curve could behave very differently than expected.

The Fed is keeping its benchmark rate at 3.50%–3.75%, retains tools to guarantee an ample supply of reserves, and has not reactivated a policy of massive asset purchases. At the same time, the Treasury has just increased its long bond purchases to improve market conditions. The combination leaves an open question for the coming months:

Can the United States keep inflation under control, finance a debt exceeding $40 trillion, and simultaneously fund the gigantic investment cycle in artificial intelligence without causing the long-term cost of capital to remain elevated?

The answer will be decisive not only for Wall Street, but will also define the returns investors worldwide will demand in the coming years, experts warn.