The United States Navy has turned back 27 ships attempting to enter or exit Iranian ports since the blockade began roughly a week ago, according to U.S. Central Command. On Sunday, a Navy destroyer attacked and seized an Iranian-flagged cargo ship that Trump said on Truth Social had attempted to evade the blockade. On Tuesday, the military seized a second vessel, the Iran-linked tanker Tifani, in international waters, the Washington Post reported.

Iran responded Wednesday by seizing two container ships in the Strait of Hormuz, the IRGC Navy announced on state media. Three additional commercial vessels came under fire in the strait the same day, CNBC reported.

The ceasefire, extended by Trump on Tuesday just hours before its expiration, is now a ceasefire in name only. Both sides have stopped bombing each other's territory. Neither side has stopped fighting at sea.

What the Blockade Is

Treasury Secretary Scott Bessent posted on social media that under Trump's orders, the Navy will continue the blockade of Iran's ports. The legal justification is sanctions enforcement: Iranian-flagged vessels and ships carrying Iranian cargo are subject to U.S. sanctions, and the Navy is interdicting them at sea rather than relying on partner nations to enforce restrictions on land.

The operational reality is broader than the legal framing. A naval blockade that turns back 27 ships is not sanctions enforcement in any traditional sense. It is a maritime quarantine that prevents Iran from importing and exporting goods by sea. Iran's parliament speaker, Mohammad Bagher Qalibaf, who led the Iranian delegation at the Islamabad talks, told Iranian state media that "a full ceasefire only has meaning if it is not violated by a naval blockade and the holding hostage of the global economy."

He has a point. The United States is simultaneously maintaining a ceasefire on land and conducting offensive naval operations at sea. The administration's position is that the blockade and the ceasefire are separate authorities operating under different legal frameworks. Iran's position is that you cannot claim a ceasefire while choking a country's economy from the water. The international law is ambiguous. The political reality is not: the blockade is why the second round of Islamabad talks has not happened.

Why the Talks Stalled

Iran notified Pakistan that it would not send a delegation for the planned second round of negotiations, the semiofficial Tasnim news agency reported. Foreign Ministry spokesman Esmail Baghaei told state media there has been "no final decision" on whether to agree to more talks, citing "unacceptable actions" by the United States, a reference to the blockade and the seizure of Iranian vessels.

The White House had planned to send Vance back to Islamabad. That trip was put on hold when Iran declined to participate, PBS reported. The diplomatic channel that the first round of talks opened has not closed, but it has gone quiet at precisely the moment when the ceasefire clock was running out.

Trump resolved the clock problem by extending the ceasefire indefinitely. He posted on Truth Social that the extension would last "until such time as their leaders and representatives can come up with a unified proposal." The extension removes the deadline pressure that made the first round of talks urgent. Whether that helps or hurts the prospects for a deal depends on whether Iran reads the extension as patience or as an open-ended license for the blockade to continue.

The Escalation Ladder at Sea

The seizure of the Iranian-flagged cargo ship on Sunday and the tanker Tifani on Tuesday crossed a line that Iran had signaled it would not tolerate. The IRGC Navy's seizure of two container ships Wednesday was retaliatory. The three vessels that came under fire in the strait the same day suggest the situation is escalating, not stabilizing.

Naval escalation in the Persian Gulf has a history that should make both sides cautious. The Tanker War of 1987-88, the last major U.S.-Iran naval confrontation, began with tit-for-tat ship seizures and ended with the accidental downing of Iran Air Flight 655, killing 290 civilians. Escalation ladders at sea are harder to control than on land because the distances are short, the reaction times are shorter, and the rules of engagement in contested waters are inherently ambiguous.

The U.S. Navy has overwhelming superiority in the Gulf. That is not in question. The question is whether the blockade produces the political outcome the administration wants (Iranian capitulation at the negotiating table) or the outcome it does not (an escalation cycle that collapses the ceasefire and restarts the air campaign).

The Economic Lever

Trump told reporters Tuesday that Iran is in a "dire economic crisis" because of the blockade. This is accurate. Iran's oil exports, already constrained by sanctions, have been reduced to near zero by the naval interdiction. Its non-oil trade, which depends on the ports of Bandar Abbas and Chabahar, has been disrupted. Consumer prices in Tehran have spiked, according to Iranian economic data reported by the Financial Times.

The administration's theory is that economic pressure will force Iran back to the table with more flexible demands. The theory has historical support: sanctions pressure was a major factor in bringing Iran to the JCPOA negotiations in 2013-2015. But the current situation is different. Iran is being blockaded by a country it just fought a war with. The domestic political dynamics favor resistance over capitulation. A regime that survives 40 days of American bombing is not likely to surrender because its ports are closed.

The blockade is leverage. Whether it is sufficient leverage to produce a deal, or whether it merely provides Iran with a justification for refusing to negotiate, is the question the administration has not yet answered.