Marco Rubio began a three-day tour of Gulf capitals in Abu Dhabi on Tuesday, the first visit by a senior US official since Washington and Tehran signed a memorandum of understanding on 14 June and held inaugural talks in Switzerland. The mission, described by Reuters as a “sensitive” assignment, is to explain the framework to Arab allies who directly absorbed Iranian retaliatory strikes during the recent war and now fear that the accord could strengthen the Islamic Republic and alter the region’s security and energy balance.

Viewed from Gulf Cooperation Council states, the memorandum contains several alarming gaps. According to officials cited in regional and international reports, the text imposes no limits on Iran’s ballistic missile programme, leaves the future of Tehran’s regional influence unaddressed, and floats a $300 billion reconstruction and development fund. Gulf diplomats also note that Iranian chief negotiator Mohammad Bagher Qalibaf has stated the Strait of Hormuz “will not return to what it was before the war” and that Iran will assume a leading role in managing the waterway through which roughly one-fifth of global oil trade passes. These capitals, which host US military bases and provided logistical support during the conflict, are seeking structural guarantees, not merely political assurances.

From Washington, the administration is pursuing a dual track. President Donald Trump has said he seeks a “fair” deal, that Iran will never possess a nuclear weapon, and that if Tehran does not act “logically” the US could “finish the job in less than a week.” Vice President JD Vance, who led the Swiss talks, described the outcome as “a very good foundation” but cautioned that a final agreement is still distant. Rubio told reporters in Abu Dhabi that he is in the region “to listen more than to talk,” that he will not ask allies to finance the reconstruction fund, and that concerns over missiles and proxies “will certainly be raised.” He also confirmed that Lebanon ceasefire negotiations are being handled separately with the Lebanese government, a point of distinction from the memorandum’s linkage to an end of hostilities with Hezbollah.

Tehran’s posture adds a layer of complexity. While agreeing to readmit international nuclear inspectors, Iranian officials have signalled that the Strait of Hormuz’s status has permanently changed, a position that directly challenges the freedom-of-navigation principle Rubio reiterated. Analysts in Washington note that the secretary of state must reassure Gulf partners without appearing to dissent from a framework that, according to informal accounts, he and other senior officials initially viewed with scepticism. Andrew Peek, a former National Security Council official, told Reuters that Rubio can point to Trump’s record of severe pressure on Iran and his readiness to resume military action if the deal collapses.

Rubio’s itinerary continues to Kuwait and Bahrain, where he will join a GCC ministerial meeting. The tour unfolds within a 60-day negotiation window referenced by US lawmakers, with Senator Ted Cruz warning that any funds released to Iran would finance extremism. The immediate test is whether the diplomatic track can convert the Swiss foundations into durable security arrangements that satisfy both the Gulf allies and the administration’s own internal critics.