The yield on the 30-year US Treasury bond touched its highest level since 2007 on Tuesday, a sign of rising worries over inflation amid the Middle East war.
The yield hit a high of 5.195 percent. The benchmark stood at 4.61 percent before the US-Israel alliance began its wave of strikes on Iran in late February.
The increase means Washington must pay higher sums to raise debt, a reflection of rising risk of persistent inflation.
Oil prices have risen around 60 percent since the start of the Middle East war, as Iran effectively closes the vital Strait of Hormuz to most tanker traffic.
Oil industry insiders have warned that crude prices could rise further if there is no agreement soon between Washington and Tehran to get shipments moving.
Iran's army warned on Tuesday it would "open new fronts" against the United States if it resumes attacks, after President Donald Trump said he had held off launching a new offensive in hopes of striking a deal.
Rising bond yields are also becoming a greater concern in Europe.
The yield on the 10-year German bund is approaching 3.2 percent, a level not seen since 2011, according to analyst John Plassard of Cite Gestion.
