U.S. Vice President Vance (left) departs for Switzerland on the 20th (local time), and Iranian Parliament Speaker Ghalibaf arrives at the Swiss negotiation venue on the 21st (local time). [AP=Yonhap News. Reposting and DB prohibited] 

The ceasefire memorandum of understanding (MOU) between the United States and Iran has encountered its first crisis just as it entered its early stages of implementation. 

The Khatam al-Anbiya Central Headquarters, which exercises integrated command over the Iranian military, announced on the 20th that it would re-blockade the Strait of Hormuz, alleging violations of the MOU by the United States and Israel. Iran specifically cited Israel's continued airstrikes in Lebanon targeting the pro-Iranian armed group Hezbollah as problematic.

This issue directly challenges the core provisions of the "Islamabad MOU," which was signed on June 17th and entered into effect on the 18th. The MOU is structured around an exchange: the United States lifting its naval blockade of Iranian ports for Iran's guarantee of safe passage for merchant vessels through the Strait of Hormuz.

The agreement stipulates that the U.S. will completely lift the naval blockade within 30 days, and Iran will guarantee safe and free passage through the Strait of Hormuz for 60 days. However, with Iran declaring a re-blockade just two days after implementation began, the most sensitive pillar of the MOU has been shaken.

Declaration of Re-blockade, but Vessels Continue to Move

The United States responded to Iran's declaration of a re-blockade not with immediate strong criticism, but by emphasizing that "actual passage is continuing."

The U.S. Central Command, which oversees U.S. forces in the Middle East, stated that Iran does not control the Strait of Hormuz and that vessel traffic continues. The Central Command also explained that U.S. forces are maintaining vigilance on the ground to ensure compliance, implementation, and effectiveness of the agreement.

This point is crucial. Iran raised the level of pressure by declaring a "blockade," but the United States did not immediately escalate this into a military confrontation. Instead, by highlighting the fact that passage through the strait was being maintained, they aimed to reduce market anxiety and preserve negotiation momentum.

Indeed, the Strait of Hormuz is a critical transit route for the global transport of crude oil and liquefied natural gas. If Iran's declaration led to an actual physical blockade, international oil prices, marine insurance, and ship operations would inevitably be destabilized once again.

Despite this, both sides maintained a dialogue. 

The U.S. delegation headed to Switzerland. Special Envoy for Middle East Steve Witcoff and Jared Kushner arrived first, and Vice President JD Vance also departed for Switzerland for negotiations. Before his departure, Vance told reporters that he expected negotiations to last about two days and expressed hope for progress on the nuclear issue and the Lebanon ceasefire.

The Iranian delegation also arrived in Switzerland.

Mohammad Bagher Ghalibaf, Speaker of the Iranian Parliament, led the delegation. The Pakistani Foreign Ministry confirmed on the 21st that face-to-face working-level talks between the two countries would be held in Switzerland. The first working-level meeting, which had been postponed once, was now scheduled to take place shortly after the re-blockade declaration.

Main Negotiations or Violation Review?

However, the fact that both sides are sitting at the same negotiation table does not mean that the main negotiations will begin immediately. 

The Iranian Foreign Ministry stated that the purpose of the meeting is not to initiate substantive negotiations, but to review the alleged MOU violations and to strongly urge the U.S. side to implement its commitments.

Iran maintains that it can only engage in nuclear negotiations once the U.S. first effectively implements economic and maritime provisions, such as lifting the naval blockade, exempting oil exports from sanctions, and allowing access to frozen assets.

The United States has different priorities. 

The U.S. views the limitation of Iran's nuclear program, the processing of highly enriched uranium, the restoration of International Atomic Energy Agency (IAEA) inspections, and a definitive ceasefire on the Lebanon front as key agenda items. This is why Vice President Vance mentioned the nuclear issue and the Lebanon ceasefire simultaneously before his departure.

Ultimately, the first point of contention at the Swiss talks will be "who implements first." 

The U.S. is seeking concrete measures regarding nuclear and security issues, while Iran wants to confirm economic compensation and the lifting of the naval blockade first. If this dispute over sequencing is not resolved, the 60-day deadline for a final agreement is likely to stall from the outset.

The Lebanon Front is the Weak Link in the MOU

The weakest link in the MOU is Lebanon. 

While the agreement stipulates that military operations must cease on all fronts, including Lebanon, Israel is not a direct party to the MOU. 

If Israel continues its military operations against Hezbollah, Iran could deem this a violation of the agreement by the United States and Israel. Conversely, the U.S. could consider Iran's inability to control Hezbollah as an incomplete implementation of the MOU.

Vice President Vance stated that the situation is improving, but also noted that it requires continuous management to ensure the safety and stability of both Israel and Lebanon. This implies that the U.S. does not view the Lebanon front as a mere secondary variable. If the Lebanon ceasefire falters, negotiations on the Strait of Hormuz and the nuclear issue could also be jeopardized.

Trump's "Hormuz Toll" Remark is a New Variable

U.S. President Trump stated that there would be no tolls in the Strait of Hormuz during the 60-day ceasefire period, and no tolls thereafter. However, he added that if a final agreement is not reached, the U.S. might impose tolls to recoup costs for services provided as a "guardian angel" to Middle Eastern countries.

This statement carries a dual message. 

One is a warning that Iran will not be permitted to impose tolls or use control of the strait as a bargaining chip.

The other is that if the final agreement fails, the U.S. could deploy new pressure tactics based on maritime security costs.

Given that the U.S. has publicly raised the possibility of imposing tolls on international waterways, this could become another point of contention in future negotiations.

The United States and Iran have signed a document to stop the war. However, the four issues of the Strait of Hormuz, the Lebanon ceasefire, the nuclear program, and sanctions relief remain unresolved.

Iran's declaration of a re-blockade has shown that the MOU is not the end of the ceasefire, but merely the starting line for implementation.

Nevertheless, the fact that both sides have agreed to attend the Swiss talks is an important signal. While the grounds for returning to war are accumulating, it indicates their intention to not yet abandon the negotiation table.

The working-level talks in Switzerland on the 21st are expected to be the first test of whether the U.S. and Iran can move beyond the MOU violation controversy and proceed to substantive nuclear and sanctions negotiations.