Hormuz closed again: Will the US-Iran MoU soon sink in the strait?

Iran has announced it is closing the Strait of Hormuz over what it says are Israeli ceasefire violations in Lebanon. The renewed fighting between Israel and Hezbollah has exposed the central weakness of the new US-Iran memorandum of understanding (MoU). The agreement was never really about the Strait of Hormuz alone. It was a broader attempt to freeze multiple conflicts at once, including the Lebanon front.

Now, only days after the deal promised relief for global energy markets and a pathway toward wider negotiations, Israel-Hezbollah clashes in Lebanon have pushed the arrangement into its first major crisis. Iran's announcement that it is closing the Strait of Hormuz while still sending negotiators to Switzerland suggests that Tehran is not yet abandoning the deal. Instead, it appears to be testing how much pressure it can exert on Washington before the next phase of negotiations begins.

Also Read: Iran shuts the doors to Strait of Hormuz; alleges US, Israeli violations of ceasefire MOU


The question is whether Lebanon becomes the graveyard of the agreement or merely the battlefield through which Iran extracts additional concessions.

The original bargain

From the outset, the memorandum was structured around a broad exchange. Iran would reopen Hormuz, allow negotiations on its nuclear program and reduce regional tensions. In return, Tehran would receive sanctions relief, access to frozen assets and a pathway toward economic normalisation. But, the agreement also envisaged an end to military operations "on all fronts, including Lebanon."

That provision was never a side issue. For Tehran, Hezbollah is not merely an ally but one of the pillars of Iran's regional deterrence architecture. Any agreement that reopened Hormuz while leaving Hezbollah exposed to continued Israeli military operations would have been politically difficult for Iran's leadership to defend at home. This explains why Iranian officials have repeatedly linked progress in US-Iran talks to developments in Lebanon. Tehran insisted hostilities in Lebanon must stop before substantive negotiations can proceed.

The weakest link

The problem is that neither Israel nor Hezbollah is formally a signatory to the US-Iran agreement. That creates a fundamental contradiction. Washington and Tehran may agree to stop fighting, but Israel's government continues to view Hezbollah as an active military threat and has publicly said that it does not consider itself constrained by every aspect of the agreement. Hezbollah, meanwhile, insists that Israeli military operations and territorial presence in southern Lebanon violate the spirit and letter of any ceasefire arrangement.

Also Read: Iranian state TV says the country's team negotiating with US over the war is going to Switzerland

The result is a classic spoiler problem. Both Israel and Hezbollah possess the capability to derail diplomatic progress even if neither Washington nor Tehran wants the agreement to collapse. Israeli Prime Minister Benjamin Netanyahu has repeatedly stated that Israeli forces will remain in southern Lebanon until security objectives are met. Hezbollah has said it will not accept unrestricted Israeli military freedom of action inside Lebanese territory. Those positions are not easily reconcilable.

Why Iran closed Hormuz but did not walk away

The most revealing development is not that Iran announced the closure of Hormuz. It is that Tehran simultaneously confirmed it would still send negotiators to Switzerland. If Iran truly intended to kill the agreement, it could have suspended talks altogether. Instead, Iranian officials framed their actions as a response to alleged violations and a demand that the United States fulfill its obligations. Iranian officials warned the memorandum itself could be jeopardised if commitments are not honoured, while still keeping diplomatic channels open. That suggests Tehran is pursuing leverage rather than walking away from talks.

Hormuz remains Iran's most powerful non-military negotiating tool. Roughly one-fifth of global oil trade traditionally passes through the waterway, making any threat to shipping immediately relevant to energy markets and inflation concerns worldwide. The reopening of the strait was one of the deal's biggest achievements and one of Washington's strongest incentives for reaching an agreement in the first place. By tying Hormuz back to Lebanon, Iran is effectively telling Washington if you want stable energy markets, you must ensure the Lebanon provisions are respected as well.

Can Tehran use Hezbollah as a pressure mechanism?

Many would think Iran possesses an enduring escalation tool because of its influence with Hezbollah. The concern is straightforward. Even if a ceasefire takes hold temporarily, Hezbollah retains the ability to challenge Israeli forces or respond to Israeli actions, creating recurring crises that can be linked to broader negotiations.

However, the relationship is more complicated than the simple proxy narrative often suggests. Hezbollah has its own political, military and domestic calculations inside Lebanon. Yet there is little doubt that Tehran sees the organisation's security as a core national interest. The structure of the memorandum itself effectively acknowledges this reality by making Lebanon central to the broader settlement.

This means Iran does not necessarily need Hezbollah to launch any major attacks. The mere possibility that the Lebanon front could deteriorate gives Tehran bargaining power. As long as instability in Lebanon threatens the wider agreement, Iran can argue that additional guarantees, stronger enforcement mechanisms or accelerated sanctions relief are necessary to sustain the diplomatic process.

The US faces the hardest choice

The burden increasingly falls on the US. The key question is not whether Tehran wants the deal. The economic incentives remain substantial. The more important question is whether Washington is willing and able to persuade Israel to operate within a framework that Iran considers acceptable. Vice President JD Vance's recent comments criticising continued escalation suggest frustration with Israel within parts of the US administration. Yet translating frustration into policy pressure on Israel is a far more difficult proposition.

If Washington cannot reduce violence in Lebanon, Tehran may conclude that the US lacks either the capacity or the political will to implement its side of the bargain. At that point, Iranian leaders would have stronger domestic arguments for slowing negotiations, maintaining pressure in Hormuz and demanding additional concessions.

Will the deal collapse?

Iran's willingness to continue to negotiate even as it announces closure of Hormuz indicates a complete collapse appears less likely than a prolonged renegotiation. Several factors point in that direction. Iran continues to participate in talks. The US continues to send senior negotiators to Switzerland. Neither side appears eager to return immediately to direct confrontation. The economic benefits of keeping the agreement alive remain significant for both governments.

What is emerging instead is a struggle over implementation. Tehran is using the Hormuz issue to increase pressure on Washington. Washington is trying to keep the diplomatic process moving despite instability in Lebanon. Israel is pursuing security objectives that do not always align with the agreement's logic. Hezbollah remains both a military actor and a strategic variable in the negotiations. The immediate future of the deal will therefore be decided less in Hormuz than in southern Lebanon.

The renewed Israel-Hezbollah fighting may not sink the US-Iran memorandum. But it has revealed that the agreement's success depends on a front that neither Washington nor Tehran fully controls. Iran's decision to threaten Hormuz while still attending talks indicates a strategy of coercive diplomacy rather than outright abandonment. Tehran appears to be using the Lebanon crisis as leverage to raise the price of its cooperation and compel the US to deliver stronger guarantees. The real test for the US is if it can prevent Lebanon from becoming the spoiler that transforms a fragile diplomatic breakthrough into another failed Middle Eastern peace effort.