US borrowing costs breach 5% as Middle East tensions fuel oil spike

The cost of borrowing money just got more expensive for the United States, and the world is watching closely. On Monday, the interest rate on 10-year Treasury bonds—the benchmark that shapes borrowing costs for governments, businesses, and households everywhere—crossed 5% for the first time since October 2023. It was a threshold traders had been tracking like a weather system, and when it arrived, it arrived with company: a global sell-off in bond markets, climbing fuel prices, and a cascade of anxiety about what comes next.

The immediate cause was oil. Brent crude, the international standard for pricing petroleum, surged to $108.50 a barrel on Monday—a jump of 3.7% in a single day. That spike came after Yemen's Houthi forces, backed by Iran, launched drone attacks on Saudi Arabia's infrastructure and seized Perim, a strategic island controlling the Bab al-Mandab strait, one of the world's most critical shipping channels. The attacks forced Saudi Arabia to shut down its east-west pipeline, a vital artery for crude exports. Traders in the kingdom warned that if the pipeline remained closed for more than a few days, Saudi Arabia would exhaust its exportable oil reserves.

This was not an isolated incident but part of a larger unraveling. The US-Israeli war with Iran, which began in late February, has been destabilizing Middle Eastern energy supplies all year. Oil started 2026 at around $72 a barrel. By April, it had climbed to $126. It fell back over the summer as ceasefire hopes flickered, but those hopes collapsed when a memorandum of understanding between the US and Iran fell apart. Now, with hostilities escalating again, the market was bracing for worse. A separate development—the postponement of talks between Gulf states and Tehran about establishing a temporary shipping corridor through the Strait of Hormuz, through which roughly one-fifth of the world's oil and gas normally flows—added another layer of uncertainty.

Higher oil prices feed inflation, and inflation is what central banks fear most. The climb in Treasury yields reflected traders pricing in that risk. The 10-year yield had been sitting at 4% earlier in the year; now it was at 5%, a move that rippled outward. UK government borrowing costs rose sharply, with 30-year yields hitting their highest level since March 1998. Gas prices in Britain climbed 5% to 208.73p per therm, the highest since December 2022. At the pump, American drivers saw petrol average 169.68p per gallon and diesel 191.68p, both new highs for the year.

The timing added to the tension. Traders were waiting for the Federal Reserve to announce its interest rate decision on Wednesday, with most expecting an increase. The Bank of England was set to decide on Thursday. The European Central Bank had already raised rates the week before. With central banks tightening policy and energy prices spiking, bond markets faced the prospect of another volatile week. Daniela Hathorn, a senior analyst at Capital.com, described the mood plainly: markets were on a defensive footing, caught between escalating Middle East conflict and increasingly hawkish central bank expectations.

Saudi Arabia's own production had already been under strain. The kingdom reported to OPEC that its crude output in August was the lowest since 1990, according to Bloomberg. Now, with the east-west pipeline closed and no clear timeline for reopening, the pressure intensified. Chris Beauchamp, an analyst at the broker IG, laid out the compounding fears: attacks on energy infrastructure, closure of key shipping routes, and the breakdown of diplomatic efforts to restart negotiations. He noted that markets had remained surprisingly calm given the circumstances, but warned that if oil prices breached the March highs—the previous peak of $126—"things could get ugly very quickly." The question now was not whether more disruption would come, but how much the system could absorb before it broke.