Oil prices jumped 6% Monday after President Trump declared his ceasefire agreement with Iran effectively dead, the clearest signal yet that diplomatic progress from mid-June has collapsed. Front-month Brent crude futures climbed to $78.63 a barrel in European trading, while West Texas Intermediate rose to $74.85. Natural gas followed, with the Dutch TTF benchmark gaining 4.8% to 49.04 euros a megawatt-hour.

The remarks came after the U.S. revoked a sanctions waiver that had permitted Tehran to sell oil, tightening supply expectations. Markets had priced in a fragile de-escalation since the preliminary deal, which had capped Iranian exports in exchange for limited sanctions relief. Trump's statement suggests the White House is now pursuing maximum pressure rather than managed containment.

Energy traders are recalibrating for sustained disruption in the Strait of Hormuz, where Iranian forces have seized tankers in past standoffs. The price move reflects a risk premium not seen since early 2024, when similar rhetoric preceded a 15% Brent rally over six weeks.

If the waiver revocation holds, Iran's export capacity could drop by 500,000 barrels daily, tightening a market already balancing OPEC+ cuts against slowing Chinese demand. The next test is whether Tehran responds with production cuts or renewed attacks on shipping infrastructure.