Global government bond yields have been climbing steadily since the outbreak of the US-Iran war, exacting a heavy fiscal toll on G7 nations, with pressures continuing to mount.

According to an analysis of government debt issuance data, G7 countries have locked in approximately $16 billion in additional sovereign debt financing costs since February due to rising bond yields. Should yields persist at current levels, projections indicate this extra expense could expand to roughly $34 billion by the end of the first quarter next year.

The United States bears the heaviest burden by far, having already incurred an estimated $10.6 billion in additional costs, with projections suggesting this figure could rise by another $21.7 billion if yields remain elevated through the first quarter of 2027. Meanwhile, energy-importing nations including the UK, Italy, Germany, and Japan have also felt the impact, as the energy supply crisis triggered by the blockade of the Strait of Hormuz has pushed up inflation expectations, consequently driving up bond yields in these countries.

Mohit Kumar, Chief European Economist at Jefferies, warned that "rising interest rates represent one of the biggest risks facing equity and credit markets." He noted that if the US 10-year Treasury yield breaks above 5%, stock markets would react negatively, as higher bond yields diminish the relative attractiveness of equities while increased borrowing costs compress corporate profit margins.

The United States Bears the Brunt as Yield Pressures Persist

The Financial Times methodology compares actual borrowing costs against pre-war interest rate levels, with the $34 billion forecast incorporating treasury issuance plans published by various governments and extrapolated based on maturity distribution patterns.

The United States, by virtue of its position as the world's largest sovereign bond market, has borne the initial impact of this yield surge.

In recent weeks, US bond yields have risen sharply as investors grow increasingly concerned about America's ballooning public debt burden and whether the Trump administration can curb the inflation surge stemming from the Iranian conflict.

Notably, Treasury Secretary Bessent has attempted to suppress yields by increasing purchases of long-dated bonds, yet these efforts have yielded limited results, with the upward yield trajectory remaining unbroken.

Currently, virtually every G7 government bond issuance across all maturities is trading at interest rates higher than February levels, directly elevating the costs governments must pay when selling new debt. The remaining G7 nations collectively account for more than one-third of this additional cost increment.

The energy supply crisis triggered by the closure of the Strait of Hormuz stands as a key driver of this yield upswing. The UK, Italy, Germany, and Japan are all major energy importers, and rising energy prices have directly lifted inflation expectations, consequently pushing up sovereign debt financing costs in these countries.

While these cost increments remain limited relative to overall public spending commitments, analysts point out they will place additional strain on already stretched government balance sheets.

Multiple Factors Converge: Yield Uptrend May Prove Sustained

Economists warn that multiple structural factors are jointly driving yields higher.

Adam Posen, President of the Peterson Institute for International Economics, noted: "Beyond inflation risks, political stability in the US, France, Japan, the UK, and even Germany faces real risks. When you layer geopolitical factors on top, that represents another genuine risk."

He added that rising defense spending, growing demand from an aging population, expanding infrastructure investment, and green expenditure growth outside the US all exert upward pressure on real interest rates.

Additionally, the massive buildout of artificial intelligence infrastructure could create a "crowding-out effect" on assets such as sovereign bonds, further pushing yields higher.

James Knightley, Chief Global Economist at ING, stated that rising borrowing costs "are not merely a fiscal sustainability issue — in the United States, they are already constraining economic activity through higher borrowing costs for households and businesses." He cautioned that the US housing market has stalled, and a steeper yield curve suggests mortgage rates could climb above 7%.

An Era of Capital Scarcity Intensifies Sovereign Debt Competition

Michel Martinez, Chief European Economist at Societe Generale, believes this trend reflects "a world where capital is no longer abundant undergoing repricing." He pointed out that sovereign borrowing is increasingly competing for savings with AI-driven investment booms and structural spending demands related to defense, energy transition, and reindustrialization.

Gianluca Salford, Head of European Rates Strategy at Morgan Stanley, views the current trend as a return to the "normal world" that predated the low-growth, low-inflation, low-rate environment of the 2010s. He commented: "This is not a situation that is clearly unmanageable... Sometimes crises are needed, but countries typically take the right measures to stay on track because there is essentially no viable alternative."

Mohit Kumar cautioned that in a high-interest-rate environment, reducing fiscal deficits becomes "more difficult." With US midterm elections and multiple European parliamentary elections approaching, governments still have incentives to pursue expansionary fiscal policies, which will further complicate debt management challenges.