Will the US announce a blockade on Iran by December 31?

Washington already blockaded Iran once this year and then lifted it, and now the market is really just pricing the odds Trump follows through on his own threat. The Strait of Hormuz has already lived through a full blockade cycle in 2026, imposed after diplomatic talks collapsed, enforced against vessels using Iranian ports, then formally lifted once a ceasefire and memorandum of understanding brought the shooting war to a pause. That sequence matters structurally: it establishes that a blockade isn't a hypothetical escalation Washington might consider, it's a policy tool the administration has already used and demonstrated willingness to deploy again. Defense officials have been explicit that the current calm is conditional, not permanent. The mechanics of a re-imposed blockade hinge entirely on the memorandum's negotiation window holding. Washington and Tehran are operating under a defined settlement period with the Strait de-mined and reopened as a good-faith gesture, and U.S. officials have publicly stated they retain full capability to reinstate an ironclad blockade if Iran fails to meet its commitments. For YES, that negotiation track needs to visibly break down, a specific, identifiable failure rather than generalized tension. For NO, the current de-escalation simply needs to hold through year-end, which requires both sides continuing to view the MOU as more valuable than renewed confrontation. The case for taking the re-blockade risk seriously is that this exact administration has already shown its threshold for reimposing maximum pressure is low, having gone from failed talks to an announced blockade once already this year in a matter of days, not months. A renewed blockade would immediately disrupt global oil flows through one of the world's most critical shipping chokepoints, reversing the fragile de-escalation and likely ending the current negotiation track entirely. Bottom line: watch for any formal Iranian violation finding or U.S. statement declaring the MOU's terms unmet. A confirmed breach declaration would sharply raise probability toward YES; continued adherence to the negotiation window keeps the contract anchored toward NO.