US Warns Iran at UN Security Council Over Strait of Hormuz: Threats, Evidence, and Fragile Diplomacy

The 2026 Strait of Hormuz crisis represents one of the most serious direct confrontations between the United States and Iran at the United Nations in decades. Here is a fact-checked timeline of the key diplomatic, military, and legal developments — from the US 'last act' warning, to Bahrain's documented evidence of Iranian attacks, to the fragile Islamabad Memorandum of Understanding (MoU) that has so far failed to stop the fighting.

US Warning to Iran: 'That May Be Its Last Act'

On June 16, 2026 — one day before the Islamabad MoU was signed — US Ambassador to the UN Mike Waltz delivered a stark warning at the Security Council. He said Iran's effective closure of the Strait of Hormuz could be its "last act," drawing a parallel to the 1979 hostage crisis . Waltz stated: "Forty-seven years ago, the Iranian regime's first act was to take dozens of Americans hostage. Now it's taking the Strait of Hormuz hostage, and with it, attempting to take the world's economy hostage. Well, colleagues, that may be its last act. We'll see."

This warning capped a multi-month diplomatic push. On May 4, 2026, the United States and Gulf allies introduced a draft UN resolution threatening sanctions or other actions unless Iran ceased assaults on vessels in the Strait, stopped imposing "illegal tolls," and disclosed all mine locations to ensure safe passage . The draft also called on Iran to cooperate with UN plans for a humanitarian corridor through the strait for essential supplies .

Bahrain's Documentation of Iranian Attacks

Bahrain acted as the lead Gulf state documenting Iranian attacks at the UN throughout the 2026 conflict. Its evidence-gathering effort was extensive and multi-layered:

Letters to the UN: Bahrain's Permanent Mission sent at least eight letters to the UN Secretary-General and Security Council President between late February and late June 2026. These letters documented specific missile and drone attacks, including statistics on the number of strikes, civilian infrastructure damage, and evidence of unlawful aggression .

UN Security Council Resolution 2817: On March 11, 2026, Bahrain circulated and secured adoption of Resolution 2817, which condemned Iran's "egregious attacks" against seven countries: Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, the United Arab Emirates, and Jordan . The resolution also condemned attacks on ships transiting the Strait of Hormuz . It was co-sponsored by 136 countries and adopted by a vote of 13-0, with Russia and China abstaining .

Post-MoU attacks: After the June 17 MoU was signed, Iran launched further attacks. On June 28, 2026, Bahrain called for an emergency UN Security Council session, documenting a "second consecutive wave of Iranian ballistic missiles and drones" targeting Bahraini territory . Bahrain's Foreign Ministry characterized the attacks as a "deliberate and systematic pattern of aggression" and a direct violation of both Resolution 2817 and the Islamabad MoU .

The Islamabad Memorandum: A Fragile Framework

The Islamabad Memorandum of Understanding (June 17 MoU) is a 14-point framework agreement signed remotely by US President Donald Trump and Iranian President Masoud Pezeshkian . Key terms include:

• Formal conclusion of hostilities between the US and Iran
• Iran's commitment to reopen the Strait of Hormuz
• US commitment to remove its naval blockade
• Commitment from both sides to negotiate a binding final deal endorsed by a UN Security Council resolution within 60 days
• Suspension of some sanctions to allow Iran to sell oil during negotiations

However, the MoU is fragile and has been partially broken. Iran briefly reopened the Strait of Hormuz but closed it again within days, citing continued Israeli strikes in southern Lebanon as a violation of the agreement — a claim denied by the US military . Bahrain and the UAE reported new Iranian missile and drone attacks in late June .

As of late June 2026, analysts described the MoU as "managing the pain rather than ending the war," with no final deal yet reached and ongoing violations on both sides . On the US domestic front, Democratic House members requested an immediate classified briefing on the MoU on July 3, demanding that the full text and any side agreements be provided to Congress .

Key Takeaways

1. The US warning was explicit: Ambassador Waltz directly linked Iran's Strait of Hormuz closure to a potential existential threat, drawing on historical hostage parallels.
2. Bahrain built an extensive evidentiary record: At least eight UN letters, a 136-country co-sponsored resolution, and detailed post-MoU attack documentation demonstrate systematic Iranian aggression.
3. The June 17 MoU is unstable: Both sides have alleged violations within days of signing, and the agreement's legal status is "decidedly murky" according to legal analysts .
4. The Strait remains contested: Despite the MoU's promise to reopen the waterway, Iran has re-closed it, and the US Navy announced a widened alternative route near Oman on June 27 .