Over nearly four decades in finance, Greg Fleming has navigated some of Wall Street's most consequential crises—from brokering Merrill Lynch's 2008 fire sale to transforming Rockefeller Capital Management into a $200 billion wealth management enterprise. Yet in a wide-ranging Bloomberg Wealth interview with David Rubenstein, the Rockefeller Capital Management CEO appeared most unsettled not by markets, artificial intelligence, or inflation, but by the ballooning U.S. national debt.

"It's a fantastic amount of money to have borrowed, even for an economy this robust and this big," Fleming said, referring to a national debt now nearing $40 trillion.

Fleming oversees more than $200 billion in client assets through the storied firm he built from John D. Rockefeller's original 1882 family office, serving some of America's wealthiest families. When Rubenstein pressed him on his single greatest concern for the U.S. economy, his answer was unequivocal.

"I'm most focused on the fiscal situation in this country," Fleming said. "We're still at relatively full employment… We have been in a good time. We run these 5, 6, 7% of GDP deficits annually, and there seems to be no impetus to change that."

He underscored a statistic that has become a flashpoint for fiscal hawks: the federal government now spends more on interest payments than on national defense. That milestone reflects not only the accumulation of debt but also the end of an era of near-zero interest rates, as the Federal Reserve's 2022–2024 rate hiking cycle sharply raised the government's borrowing costs on newly issued Treasury securities.

The Scale of $40 Trillion

Fleming's reaction is anchored in a mounting series of fiscal milestones. The national debt crossed $39 trillion in mid-March, with net interest payments projected to surpass $1 trillion in fiscal year 2026—nearly triple the $345 billion the government paid in interest at the onset of the pandemic in 2020.

By April, debt held by the public exceeded 100% of GDP for the first time since World War II, meaning total government obligations outstripped the size of the entire U.S. economy. Brookings Institution economist Jessica Riedl calculated that the ratio could climb to 137% within a decade, a trajectory that would eclipse the debt's postwar peak and remain at elevated levels indefinitely—unlike the temporary wartime surge that preceded it. In the post-World War II period, debt-to-GDP ratios fell steadily, aided by sustained economic expansion and a growing labor force. Today's trajectory is driven primarily by structural forces, including mandatory spending growth in Social Security and Medicare, which the Congressional Budget Office projects will account for the largest share of federal spending increases over the coming decade.

Fleming told Rubenstein that the debt landscape poses a particular challenge for new Fed Chair Kevin Warsh, who inherited a complex set of economic crosscurrents. Artificial intelligence adoption is "moving faster than even I thought," Fleming noted, and could exert a disinflationary effect as companies deploy AI agents to enhance productivity. Still, he described a "very complicated picture," in which productivity questions collide with an energy shock and a fiscal deficit that "clearly could put pressure on rates, particularly on the long end."

On a podcast in late 2025, Fleming had suggested that AI might help the U.S. grow its way out from under the debt even amid rising deficits. But speaking with Rubenstein, that optimism had visibly narrowed: he acknowledged that AI is, at best, one variable among several—competing against an energy shock and unchecked deficit spending rather than serving as a silver bullet.

Recent research supports that more measured stance. The St. Louis Fed analyzed nearly 490,000 corporate earnings calls and found a sharp increase in mentions of AI-related productivity, yet almost no corresponding signal in macroeconomic data.

A Longstanding and Deepening Concern

Fleming's alarm is not a recent development. He has voiced strikingly similar warnings over several years, suggesting the debt has evolved from a background concern into a central preoccupation.

As far back as October 2023, Fleming told Bloomberg's David Westin that the "U.S. debt situation is definitely a concern," predicting that interest payments would overtake military spending by 2027. That threshold materialized sooner than he anticipated, becoming a permanent feature of the federal budget by 2024. At the time, he flagged deficits running at approximately 8% of GDP during a period of economic expansion and full employment as historically anomalous.

His warnings mirror a broader shift across the wealth management industry, where advisors are particularly attuned to fiscal risk given their responsibilities stewarding multigenerational family wealth. A 2024 industry survey found that 48% of financial advisors ranked the national debt as America's "most urgent" policy problem—above immigration, tax policy, and geopolitical conflict.

"If one of our clients had the balance of income and expenses that the U.S. government has, they would be broke," one advisor remarked.

That observation captures why Fleming's comments carry weight. His daily work involves counseling ultrawealthy families on preserving fortunes across generations through prudent spending and avoiding excessive leverage. Applying that same framework to Washington, he suggested to Rubenstein, yields an uncomfortable conclusion.

Fleming stopped short of forecasting a crisis and said he remained optimistic about long-term U.S. wealth creation, noting in the same interview that new "growth cities" continue to generate substantial fortunes for the families his firm serves.

Nevertheless, his framing made clear that he regards the debt trajectory as a structural risk—one that could reshape interest rate and inflation dynamics for years to come, and one that even AI-driven productivity gains may only partially mitigate.

Rockefeller Capital Management did not respond to a request for comment.

This story was originally featured on Fortune.com.