With letters to the UN Security Council, the United States and Israel are attempting to provide international legitimacy to the attack they launched on February 28 against Iran, invoking Article 51 of the UN Charter on lawful self-defense, as well as the need to eliminate the threat posed—according to their claims—by Iran’s policies to the very existence of Israel and to regional stability.

The two letters were submitted to the UN on March 10 and include all the arguments which, according to the two countries, led to the February 28 operation and justify it due to the scale of the threat. The letters detail not only Iran’s steps toward acquiring nuclear weapons and strengthening its ballistic arsenal, but also attacks carried out over time against American and Israeli targets, as well as the destabilizing actions of the Iranian regime’s “proxies.” They also stress that military action followed the failure—attributed to Tehran—of efforts for a peaceful resolution.

What the US letter states

The US letter notes that the United States launched military operations “to defend the American people from attacks and ongoing threats from the Islamic Republic of Iran, in coordination with our ally, Israel. These operations were conducted to protect United States Armed Forces in the region, to ensure the free flow of maritime commerce through the Strait of Hormuz, and to protect our regional allies and partners from Iran and its proxies.”

The letter further states that “the Islamic Republic of Iran has rejected peaceful coexistence and has chosen international armed conflict with Israel, waging an unprovoked religious war of annihilation against a former friendly UN member state located hundreds of miles from its borders. Since June 2025, the regime has also massively expanded its production of ballistic missiles, aiming to overwhelm regional air defenses and create a protective shield for its efforts to reconstitute its nuclear program, which it refuses to abandon. Exploiting the international legal system, the Iranian regime systematically seeks to conceal its unlawful actions and evade accountability, including through the use of proxies such as Hamas, Hezbollah, and the Houthis.”

The US recalls that in recent years it has faced more than one hundred attacks from Iran or its proxies, referencing incidents ranging from the 444-day hostage crisis at the US embassy, to the bombing of the Marine barracks and the Khobar Towers (1996), to attacks with improvised explosive devices and other strikes against Americans in Iraq, as well as support for Hamas’s atrocities on October 7, and ongoing indiscriminate missile and drone attacks against civilians across the Middle East and beyond.

“The United States has now acted to address the ongoing threat posed by the Iranian regime, because peaceful measures have once again been attempted and exhausted… The United States retains the right, under Article 51 and customary international law, to take further action in self-defense and in the collective self-defense of its allies and partners, if necessary,” the letter concludes.

What Israel’s letter states

Israel, in its letter signed by Foreign Minister Gideon Sa’ar, emphasizes that “for decades, the Iranian regime and its leaders have openly declared that their goal is the destruction of the State of Israel. This has never been mere rhetoric, but an operational plan pursued through a continuous campaign of hostilities, including via its network of terrorist proxies, as well as through the relentless pursuit of nuclear weapons and other weapons of mass destruction, and its long-range missile program. Iran has launched direct ballistic and cruise missile attacks against Israel and has conducted numerous covert and overt hostile operations—on land, at sea, in the air, and in cyberspace—as part of the ongoing armed conflict it is waging…”

According to Israel, Tehran, “despite continuous diplomatic efforts by the international community and the consistent, necessary, and proportionate military action undertaken by Israel (June 17, 2025)… has continued to pursue its declared objective of destroying the State of Israel and to wage an ongoing armed conflict against it… while also accelerating, covertly and rapidly, its efforts to acquire nuclear weapons and expand its long-range missile program.”

Explaining the timing of the latest strike, Israel states that: “Without immediate action, Iran’s nuclear and missile capabilities would soon have reached a stage where effective defensive intervention would no longer be possible. Failure to act now, after exhausting other reasonable measures, including extensive diplomatic efforts led by the United States, would permanently eliminate Israel’s ability to defend itself against this existential threat.”

Citing Iran’s attacks against countries in the region, including Gulf states and beyond, Israel argues that “Iran’s recent actions further underscore that its aggression constitutes an immediate threat not only to Israel, but also to regional and international peace and security. The regime’s brazen attempts to legitimize its unlawful and indiscriminate attacks against civilians on the territory of multiple states have rightly been rejected and fully condemned.”

Israel also highlights the risk posed by Iran’s threats to close the Strait of Hormuz and disrupt global maritime navigation, as well as Iran’s violations of UN Security Council Resolution 2231 (2015), which required it to suspend nuclear-related activities, including the construction of enrichment facilities, and prohibited activities related to ballistic missiles and the transfer of weapons to proxy terrorist organizations.

The letter also makes reference to Iran’s internal situation, stating that “the regime has also massacred its own citizens, the brave people of Iran, who have sought freedom from its tyrannical rule, committing mass atrocities against civilians. Operation ‘Rising Lion’ is not directed against the people of Iran, who for many years have sought greater freedom and dignity in the face of oppression. Their struggle against tyranny and pursuit of freedom deserves the support of the international community.”

According to Israel, “weakening the military capabilities of this despotic regime, in order to eliminate the existential threat to Israel, may also contribute to creating the conditions for the Iranian people to free themselves from the chains of tyranny and pave the way for a safer and more peaceful region and world.”

Finally, Israel warns that “in accordance with its right and duty to defend itself and its citizens, it will continue to take all necessary measures and conduct its military operation in accordance with international law, including the principles of distinction, proportionality, and the obligation to take all feasible precautions to minimize civilian casualties,” calling on the Security Council to condemn “Iran’s hostile actions across the region and its decades-long destabilizing activity, which constitute a serious threat to regional and international peace and security.”