TEHRAN — Iranian authorities have escalated both action and rhetoric over maritime control in the Strait of Hormuz, warning that safe passage will be provided only through coordination with Tehran. The latest status in the waterway is fast emerging as a critical stress test for the fragile Iran-US memorandum of understanding less than a fortnight after its signing.

In an X post on Friday, Deputy Foreign Minister Kazem Gharibabadi said, "Safe passage through the Strait of Hormuz cannot be guaranteed under ambiguous arrangements, parallel routes or decision-making outside of Iran's considerations as a coastal state." He added that any credible framework must be based on coordination with Iran, citing clause five of the Islamabad memorandum. The diplomat warned that a lack of such coordination will result in "the suspension of the designated parallel route."

The remarks followed a series of warnings by Iran's Islamic Revolutionary Guard Corps (IRGC) this week, which said the use of shipping lanes outside those specified by Tehran were "unacceptable and very dangerous," and that vessels must liaise directly with the IRGC via a designated radio channel. 

On Thursday, according to state media, Iranian authorities also turned back at least three tankers attempting to transit via "unauthorized routes," in what appears to be reflective of a policy under which Iran is treating maritime security not as a technical issue resolved in the memorandum but as a strategic lever.