Government borrowing costs across major economies climbed further on 18 August 2026 to levels unseen in decades, as optimism over a lasting US-Iran truce collapsed. The renewed selloff in bond markets came after the ceasefire lapsed with no progress on reopening the Strait of Hormuz, a corridor notes carries roughly a fifth of the world's oil and liquefied natural gas trade.
Sentiment worsened further after President Donald Trump warned he would bomb Oman if the country "got in the way" of negotiations, a remark that rattled investors already bracing for higher energy costs and stickier inflation. Markets now fear that renewed conflict risk will keep interest rates elevated for longer, compounding pressure on government debt already strained by rising defence budgets in Europe and the United Kingdom.
How high have yields climbed?
The 30-year US Treasury yield rose to 5.324% on 18 August 2026, its highest level since June 2007, according to the original reporting, while separately put the figure at 5.327% during Tuesday's trading. The 10-year US Treasury yield rose to 4.736%, with citing a close figure of 4.739%.
In Japan, the 10-year government bond yield climbed 2.5 basis points to 2.945%, a three-decade high, a move confirmed by , which also reported that Japan's 2-year bond yield jumped to 1.7%, its highest since May 1995. In the UK, 10-year gilt yields rose 2.6 basis points to 5.076%, while Germany's 10-year Bund yield reached its highest level since 2011 and France's equivalent hit its highest point in at least 16 years, with describing it as a 17-year high.
Why are inflation fears growing?
Bond yields move inversely to prices, so the widespread selloff reflects investors demanding greater compensation for holding long-term government debt. According to , oil prices climbed above $90 a barrel as talks on restoring the US-Iran truce stalled, adding fresh inflationary pressure across global markets.
Dan Coatsworth, head of markets at AJ Bell, said the rise in long-dated yields cannot be explained by interest rate expectations alone.
Rising long-dated bond yields are not driven solely by expectations of higher interest rates and inflation fears. They can also reflect concerns around high levels of government borrowing and investors demanding greater compensation for the risks of holding long-dated government bonds.
Neil Wilson, a Saxo UK investor strategist, pointed to a broader combination of pressures weighing on fixed income markets.
We are seeing bond yields across developed markets strike multi-year highs as fixed income investors grow nervous about a range of factors, from inflation and the Iran conflict to deeper structural concerns and fiscal worries. Issuance is clearly a factor – both on the government side (they can't stop spending!) and on the corporate side (AI capex).
How does this connect to earlier warning signs?
The latest surge extends a pattern that has been building for months. Back in March 2026, UK borrowing costs had already surged to their highest since 2008 as markets priced in as many as three interest rate hikes amid the escalating Iran conflict, with the UK's February budget deficit unexpectedly rising to £14.3bn. By May, UK 30-year borrowing costs had climbed to their highest since 1998 amid a separate oil price surge and political uncertainty. Japan's own tightening cycle had already pushed its interest rate to 1%, the highest since 1995, in June, a move directly linked at the time to inflation stemming from the US-Iran war.
What does this mean for households?
Higher government bond yields typically feed through into the cost of everyday borrowing. CNBC has noted that the US 10-year Treasury yield serves as the main benchmark for mortgages, auto loans and credit card debt, meaning sustained rises could squeeze household budgets well beyond financial markets. This mirrors earlier warnings from March 2026, when UK mortgage rates were expected to rise even after Trump had briefly paused strikes on Iran, as inflation concerns continued to drive market pricing.
What happens next?
The US-Iran ceasefire was due to lapse on Monday, 17 August 2026, with reporting that no formal negotiations or agreement were in sight as of that date. Adding to pressure on debt markets, the US Treasury is scheduled to sell $25bn of new 30-year bonds, following an auction last week that cleared at the highest yield for that maturity since 2001, according to a report cited by The News International. Oman's foreign ministry had earlier, on 17 August 2026, welcomed the announcement of a ceasefire between Iran and the United States, while US and Qatari officials said on 4 August 2026 that progress was being made toward reopening the Strait of Hormuz — progress that now appears to have stalled.
Key Facts
- US 30-year Treasury yield hit 5.324%-5.327% on 18 August 2026, the highest since June 2007
- Japan's 10-year government bond yield reached 2.945%, a three-decade high, while its 2-year yield hit 1.7%, the highest since May 1995
- UK 10-year gilt yields rose to 5.076%; Germany's 10-year Bund yield hit its highest since 2011 and France's reached a multi-year peak
- Oil prices climbed above $90 a barrel as ceasefire talks stalled
- The US Treasury is due to sell $25bn of new 30-year bonds after last week's auction cleared at the highest yield since 2001
