US Fires on Iran-Flagged Tankers as Washington Awaits Response on Peace Deal

On the morning of May 8, 2026, U.S. fighter jets struck the smokestacks of two Iranian-flagged oil tankers attempting to dock at an Iranian port in the Gulf of Oman, disabling both vessels in what U.S. Central Command described as enforcement of the ongoing American naval blockade [1]. Hours later, in Rome, Secretary of State Marco Rubio told reporters the United States expected Iran to respond that same day to a proposed peace framework [2]. The juxtaposition — precision munitions hitting tankers while diplomats awaited a phone call — captured the central contradiction of American policy toward Iran ten weeks into a war that has rattled global energy markets and strained constitutional limits on presidential war-making authority.

What Happened on May 8

CENTCOM said U.S. forces fired "precision munitions into their smokestacks, preventing the non-compliant ships from entering Iran" [3]. The two tankers were described as unladen — carrying no cargo — but were judged to have violated the U.S. blockade by attempting to reach an Iranian port. Video released by the military showed an F/A-18 Super Hornet conducting the strikes [4].

The incident followed a night of broader hostilities. Late on May 7, CENTCOM reported that it had thwarted Iranian attacks on three U.S. Navy warships in the Strait of Hormuz, accusing Iran of launching missiles, drones, and small boats in what it called an "unprovoked attack" [5]. Iran disputed that characterization. Tehran said its forces had fired in response to U.S. targeting of an Iranian tanker, and accused Washington of striking first [6].

An Iranian news agency affiliated with the judiciary reported at least one sailor killed and 10 injured aboard a cargo vessel that caught fire during overnight U.S. strikes [1]. The Pentagon has not confirmed these casualty figures, nor has it characterized the action as a use of lethal force against foreign nationals. The nationalities of the crew members remain unconfirmed in public reporting, though China's Foreign Ministry separately expressed concern about a Marshall Islands-registered vessel with Chinese crew in the area [7].

The Blockade's Legal Foundations

The U.S. naval blockade of Iranian ports was formally announced on April 13, 2026, after peace talks in Islamabad collapsed [8]. Joint Chiefs of Staff Chairman Gen. Dan Caine described the mission as a blockade on Iran's ports and coastline — not on the Strait of Hormuz itself — with enforcement extending to other theaters, including the Pacific [9].

The legal authority underpinning the blockade is contested. The Trump administration has not obtained a UN Security Council resolution authorizing the use of force, nor has it invoked Article 51 self-defense provisions under the UN Charter in the traditional sense. Instead, the Pentagon has relied on a "right-of-visit" under international maritime law, classifying targeted vessels as stateless or sanctions-violating to broaden its authority to stop, board, and fire upon them [8].

International law scholars have challenged this framing. Under the United Nations Convention on the Law of the Sea (UNCLOS), Articles 38 and 44 establish that states bordering international straits may not suspend or impede the right of transit passage [10]. While the U.S. blockade formally targets Iranian commerce rather than all strait traffic, the practical effect has been to disrupt broad categories of shipping. Neither the United States nor Iran has ratified UNCLOS, but its core provisions are widely considered codifying customary international law, making them binding regardless of ratification [10].

The question of whether an armed conflict formally exists between the U.S. and Iran — a prerequisite for a legal blockade under the law of armed conflict — remains unresolved. The Trump administration simultaneously maintains that a ceasefire is in effect and that it is conducting blockade enforcement operations, positions that sit uneasily together under international humanitarian law [11].

The War Powers Fight in Congress

The Trump administration notified Congress of the conflict on March 2, starting the 60-day clock under the War Powers Resolution [12]. That deadline expired on May 1. The administration's response has been to argue that the April 7 ceasefire "terminated" hostilities, resetting or eliminating the requirement for congressional authorization — a claim disputed by lawmakers and legal experts on both sides of the aisle [13].

President Trump told reporters he considers seeking congressional authorization under the War Powers Act "unconstitutional" and falsely claimed other presidents had not done so [13]. Democratic lawmakers have noted that the statute contains no provision allowing for a pause once the deadline has started, and that ongoing blockade enforcement and exchanges of fire undermine the claim that hostilities have ceased [14].

Within the Republican Party, dissent has been limited but notable. Sen. Rand Paul (R-KY) has been the sole Republican to vote with Democrats on war powers measures, co-sponsoring legislation to limit Trump's authority to wage war in Iran [15]. Sen. Susan Collins (R-ME) stated that congressional authorization would be needed for boots on the ground or hostilities lasting beyond 60 days [15]. Sen. John Curtis (R-UT) wrote that he would not support ongoing military action beyond the 60-day window without congressional approval [15].

Rep. Tom Barrett (R-MI) introduced an Authorization for Use of Military Force specifically designed to "limit and wind down" the conflict and restore congressional war powers authority [16]. Despite these individual objections, the Senate has voted five times to advance debate on constraining the war, and each time Republicans — with only Paul dissenting — have blocked the measure [15].

Senate Majority Leader John Thune and House Speaker Mike Johnson have refused to support efforts to check the president's authority [15].

The Peace Deal Framework

The proposal Iran was expected to respond to on May 8 is a 14-point memorandum of understanding (MOU) negotiated through a combination of direct and mediated channels. Trump envoys Steve Witkoff and Jared Kushner have been involved in the talks, with Pakistan serving as an intermediary [17].

No official text has been made public, but reporting from multiple outlets has outlined its core terms [17][18]:

Nuclear provisions: Iran would commit to a moratorium on nuclear enrichment for 12 to 15 years, after which it could enrich up to 3.67% purity. Iran would pledge never to seek a nuclear weapon, commit not to operate underground nuclear facilities, and accept enhanced inspections including snap visits by UN inspectors [18].

Sanctions relief: The U.S. would commit to a gradual lifting of sanctions and the phased release of billions of dollars in frozen Iranian funds held internationally [18].

Strait of Hormuz: Both sides would lift restrictions on transit through the strait. The MOU would declare an end to the war and begin a 30-day negotiation period for a detailed agreement covering the strait, the nuclear program, and sanctions [17].

Contingency: Many terms are contingent on a final agreement being reached within the 30-day window, leaving open the possibility of renewed hostilities if talks collapse [17].

Iran's Foreign Ministry said Thursday it was reviewing messages from the U.S. received via Pakistani mediators but had not reached a conclusion [2]. Rubio, speaking alongside Pope Leo XIV in Rome, said: "We'll see what the response entails. The hope is it's something that can put us into a serious process in negotiation" [2].

Iran's Case: "Reckless Military Adventure"

Iran's Foreign Minister Abbas Araghchi posted on X: "Every time a diplomatic solution is on the table, the U.S. opts for a reckless military adventure" [3]. The Foreign Ministry condemned the strikes as "hostile" military action that violated the ceasefire [1].

The strongest version of Iran's argument rests on several points. The tankers were attempting to reach an Iranian port — Iranian vessels approaching their own territory. The U.S. blockade lacks UN Security Council authorization, and under UNCLOS and customary international law, armed interdiction of vessels on the high seas or in international straits without such authorization is legally questionable [10]. The administration's insistence that a ceasefire remains in effect while simultaneously firing on ships creates a logical contradiction: if the ceasefire holds, the strikes are a violation; if it doesn't, the War Powers clock is running [14].

Iran's own actions, however, undermine its claim to legal high ground. The Islamic Revolutionary Guard Corps closed the Strait of Hormuz to international shipping in late February 2026, laid sea mines, boarded and attacked merchant vessels, and fired on tankers from multiple countries — including an ADNOC tanker belonging to the UAE, which the Gulf Cooperation Council condemned as "piracy" [19][20]. Iran's creation of a "Persian Gulf Strait Authority" to charge tolls on vessels transiting the waterway has no basis in international law, as UNCLOS explicitly prohibits coastal states from levying charges on transit passage [10].

Oil Markets and Economic Exposure

The conflict's most immediate global impact has been on energy markets. Before the war, approximately 20.5 million barrels per day of oil and petroleum products transited the Strait of Hormuz, representing roughly one-fifth of global seaborne oil supply [21]. Iran's closure of the strait beginning in late February reduced that flow sharply.

Source: EIA / Congressional Research Service

Data as of May 8, 2026CSV

Brent crude, which traded near $65 per barrel before the war began on February 28, surged past $120 per barrel after the strait was closed in early March [22]. Following the May 7-8 clashes, Brent rose as high as $103.70 before settling at $101.12 — approximately 40% above pre-war levels [23]. WTI crude stood at $109.76 as of early May, up 87.6% year-over-year [24].

Source: FRED / EIA

Data as of May 4, 2026CSV

The International Energy Agency has described the situation as the "greatest global energy security challenge in history" [22]. Maritime insurers have suspended or repriced war-risk coverage for strait transits. War-risk premiums rose from 0.125% to as high as 1% of a ship's insured value per transit, adding hundreds of thousands of dollars per shipment [25]. The World Economic Forum reported that governments are increasingly becoming "insurers of last resort" for Gulf shipping [26].

Asian stock markets fell after the May 8 strikes: Japan's Nikkei 225, South Korea's KOSPI, and Hong Kong's Hang Seng each declined more than 1%. The S&P 500 fell approximately 0.4% [23].

The estimated daily production shortfall caused by shipping paralysis in the strait reached 14.5 million barrels [23], though partial reopening efforts have recovered some volume.

GCC Reactions

The Gulf Cooperation Council has focused its condemnation primarily on Iran. The GCC Secretary General condemned "in the strongest terms" Iranian attacks on an Emirati ADNOC tanker in the strait, calling such actions "piracy and a serious threat to the security of maritime routes" and a "flagrant violation of the relevant Security Council resolutions" [20]. The GCC expressed "full solidarity" with the UAE [20].

The UAE's Defense Ministry confirmed three people wounded from Iranian missile and drone attacks on May 4, when Iran struck at UAE territory — an escalation that broadened the conflict beyond U.S.-Iran bilateral hostilities [27]. Italian Prime Minister Giorgia Meloni has been working to build a joint EU-GCC diplomatic strategy on the conflict [25].

Does Coercion Produce Concessions?

The historical record offers limited encouragement for those who believe naval pressure will bring Tehran to the table. During the 1980-1988 Tanker War — the most direct precedent — Iraq attacked Iranian shipping specifically to provoke Iran into closing the Strait of Hormuz, hoping to trigger international intervention against Tehran [28]. Iran threatened closure repeatedly but never followed through, recognizing that it too depended on the sea lanes for oil exports [28].

The United States intervened directly in 1987 with Operation Earnest Will, escorting re-flagged Kuwaiti tankers through the Gulf [28]. The conflict culminated in the USS Vincennes' downing of Iran Air Flight 655 in July 1988, killing 290 civilians — a tragedy that, combined with war exhaustion, hastened Iran's acceptance of a UN-brokered ceasefire [28]. The lesson Tehran drew was not that naval pressure worked as diplomacy, but that American military operations in the Gulf carried unacceptable risks of catastrophic escalation.

More recently, the 2019-2020 tanker incidents in the Gulf — in which the U.S. blamed Iran for attacks on six commercial vessels — did not produce diplomatic concessions. Instead, they hardened positions on both sides and contributed to the collapse of remaining channels between Washington and Tehran after the U.S. withdrawal from the JCPOA [29].

The current situation differs in that a formal peace framework is on the table. But the simultaneous application of military force and diplomatic engagement creates what analysts call a credibility paradox: the strikes may demonstrate resolve, but they also validate Iran's narrative that the U.S. is not negotiating in good faith — a narrative that strengthens hardliners in Tehran who oppose any deal.

What Comes Next

As of May 8, the situation remained in flux. The ceasefire, now more than a month old, has not been formally abandoned by either side, even as both exchange fire in the strait. The 14-point MOU represents the closest the two sides have come to a framework for ending the war, but its terms remain contingent and its acceptance by Iran uncertain.

The constitutional question is equally unresolved. The 60-day War Powers deadline has passed, Congress has failed to assert its authority, and the administration continues military operations under a theory of terminated hostilities that the facts on the ground contradict daily.

With Brent crude above $100, shipping insurance markets in turmoil, and the IEA warning of the worst energy security crisis in history, the economic costs of continued ambiguity are mounting. The question is whether the combination of military pressure and diplomatic outreach will produce a breakthrough — or whether, as in past confrontations with Tehran, it will produce only escalation.