European natural gas prices rose nearly 4% on Monday to their highest level since January 2023 after the US launched Operation Economic Outcast, an “unprecedented” sanctions campaign aimed at isolating Iran from the global financial system. The September futures contract at the Dutch-based TTF, Europe’s benchmark gas trading hub, climbed around 4% to €68.45 ($79.85) per megawatt-hour. US Treasury Secretary Scott Bessent said the campaign targets Iran’s aviation, shipping, gold, technology, and digital asset sectors, and warned that entities facilitating money laundering for Tehran would be permanently removed from the US dollar system. He also signaled that a major financial institution could face sanctions by the end of the week. The measures followed US President Donald Trump’s warning that Washington could sanction countries continuing to trade with Tehran. Iran rejected the threats as a sign of desperation and said further sanctions would not force it into submission. European gas markets remain exposed to Middle East disruptions because tensions have kept the Strait of Hormuz largely closed and delayed Qatari liquefied natural gas shipments to Europe. Stronger cooling demand during a summer heatwave has also slowed inventory replenishment, raising concerns over storage levels and whether Europe will have an adequate supply buffer before the winter heating season.