While investors fixate on the AI boom, a warning from a group of Wall Street bankers whose job is to help the U.S. government borrow went unnoticed.

In minutes released Aug. 5, the Treasury Borrowing Advisory Committee—a panel of senior bond dealers and investors, known as TBAC, that advises the Treasury on its own funding—warned that at current auction sizes, the government faces a $1.45 trillion funding shortfall in fiscal 2027–28.

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What that means takes a primer to understand how Washington actually borrows. The Treasury doesn't take out one huge annual loan, rather, it raises cash by selling debt at regularly scheduled auctions. The shortest-dated IOUs, sometimes called "T-bills," come due in a year or less, while the longer-dated notes and bonds — known as "coupons" — run anywhere from two to 30 years.

The T-bills offer Washington, now, a rare opportunity to borrow money for the cheap.

At the time of writing, the three-month bill yielded around 3.8%, while the 10-year Treasury yield sat around 4.6%, and the 30-year at a multi-decade high above 5%. So what Treasury Secretary Scott Bessent has done is lean unusually hard on the cheaper rate today to finance a roughly $2 trillion annual deficit. That holds down reported borrowing costs but leaves the government more exposed to inflation and rising rates.

The committee's own minutes hint at the strain: rising interest costs drove the biggest jump in Treasury outlays this year, up $120 billion. The government's total debt on interest alone now runs over $1 trillion annually, more than the United States spends on national defense.

That worries Jon Hilsenrath, the veteran Federal Reserve watcher who spent decades at The Wall Street Journal and now runs his own advisory firm, Serpa Pinto Advisory.

"If there are cracks that show up in the financial system over the next few years, I've been expecting them to show up in Treasury debt," he said in an interview. "If you look at any serious financial crisis, all you've got to do is follow the debt." In 2008, that meant mortgages, but today, he argues, "all the growth has been in federal debt."

The even bigger problem, Hilsenrath says, is a collision taking shape with the Treasury and the Fed. Just as Treasury is likely forced back toward longer-term bonds, the Fed under new Chair Kevin Warsh is moving to shrink its own balance sheet. The TBAC minutes note dealers expect the Fed's holdings to drift toward shorter maturities and more bills—and Hilsenrath says a Warsh-appointed new Fed committee, due to report on the balance sheet in December, will almost certainly conclude the Fed is overstocked on long-term Treasuries and must wind them down. So that would mean two waves of long-term supply, converging, with fewer buyers.