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Top Questions

What was the significance of the 2025 snapback sanctions deadline?

What is the main goal of U.S. Pres. Donald Trump’s negotiations with Iran?

Why did Israel attack Iran in June 2025?

Why did Iran stop being a U.S. ally?

Why did President Trump withdraw from the previous Iran nuclear deal, the Joint Comprehensive Plan of Action (JCPOA), in 2018?

Why does Iran want a nuclear program?

Did the U.S. declare war on Iran?

In his second term in office U.S. Pres. Donald Trump made it one of his first foreign policy priorities to finalize a deal with Iran, limiting its nuclear program and the reach of its military (including through ballistic missiles and support for the country’s allies in the Axis of Resistance). The push—amid the far-reaching Israel-Hamas War that has destabilized the entire region and resulted in tremendous setbacks for Iran and its allies—comes seven years after Trump pulled out of the previous nuclear deal, the Joint Comprehensive Plan of Action (JCPOA) negotiated under his predecessor, Pres. Barack Obama. According to Trump, that deal merely delayed Iran’s development of nuclear weapons and “it didn’t bring calm, it didn’t bring peace, and it never will.”

• U.S.-Iran Relations: A timeline of betrayal, rhetoric, and bloodshed.

The Trump administration initially pursued the negotiations with a strict timeline. Under the terms of the JCPOA, which were still recognized by the international community despite the U.S. withdrawal from the agreement, the United Nations had until October 18, 2025, to reimpose sanctions on Iran if it were found to be non-compliant. This “snapback sanctions” mechanism, which was designed to be swift and prevent Iran’s allies from protecting Iran, was a key point of leverage that the United States would no longer have after October.

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But the negotiations came to an abrupt end in June and the subsequent series of events led ultimately to the snapback sanctions being reimposed. After a breakdown in the talks, the International Atomic Energy Agency (IAEA) declared Iran non-compliant for the first time since 2005 after a vote put forward by the United States, Britain, France, and Germany, four of the six main signatories to the JCPOA. Although Trump posted on Truth Social on June 12 that the United States “remain[s] committed to a Diplomatic Resolution to the Iran Nuclear Issue! My entire Administration has been directed to negotiate with Iran,” Israel launched an attack on Iran just hours later. The 12-day Israel-Iran Conflict killed top Iranian military leaders and nuclear scientists, caused significant damage to Iran’s military and nuclear infrastructure, and in its final days it involved U.S. strikes on Iran’s most important nuclear facilities.

In response to the conflict Iran’s parliament voted to suspend the country’s cooperation with the IAEA, prompting the United Kingdom, France, and Germany to trigger the JCPOA’s snapback mechanism in August. After the UN Security Council failed to pass a resolution, supported by only 4 of its 15 members, to stop the snapback sanctions, UN sanctions were set to resume at the end of September.

The sanctions put the Iranian rial into a freefall, prompting a destabilizing outbreak of protests in late December. After the protests were brutally repressed—with people killed by gunfire on a scale unseen since World War II—the United States moved naval and air force assets into the region. Amid the rising tensions the United States and Iran began resuming negotiations in February 2026.

But why do experts assume that Iran is seeking a nuclear weapon? And why is the United States so concerned if other countries already have nuclear weapons? Britannica has the background and context you need—and more—to understand the high-stakes negotiations.

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Why does Iran have a nuclear program?

Iranian officials claim that their nuclear program is for civilian purposes, but experts say that the country enriches uranium and stockpiles it beyond levels needed for any civilian purpose. Observers generally agree that Iran wants the capability to produce a nuclear weapon, partly to position itself against ongoing threats to the regime’s security. Here is some background on Iran’s security stance:

Why are the United States, Israel, and other countries so concerned?

If Iran develops a nuclear weapon, it would be the first country to do so since North Korea in 2006, and it might encourage other countries to follow suit. Building a nuclear weapons program is against international convention, which attempts to limit and prevent the extremely dangerous possibility of nuclear proliferation. Some countries, including the United States and Israel, also worry that the possession of nuclear weapons might make it impossible to face down a regime that leads vitriolic chants of “Death to America” and “Death to Israel.”

  • Treaty on the Non-Proliferation of Nuclear Weapons (NPT):
    • This agreement of international consensus forbids the development of nuclear weapons. Iran is a signatory to the treaty.
  • List of States with Nuclear Weapons:
    • Only a handful of countries currently possess nuclear weapons, and only three of them became nuclear states after the NPT was concluded in 1968.
  • Joint Comprehensive Plan of Action (JCPOA):
    • The previous U.S.-led deal limiting Iran’s nuclear capabilities had broad support, including several European powers as well as Russia and China. The United States unilaterally withdrew in 2018 and many of the JCPOA’s provisions expired in October 2025.
  • Issues Affecting Nuclear Power:
  • International Atomic Energy Agency (IAEA):
    • This autonomous intergovernmental organization monitors nuclear programs to ensure they are used for peaceful purposes, but it requires the cooperation of the monitored countries. Cooperation with the IAEA was a component of the JCPOA agreement.
  • Israel-Iran Conflict:
    • The tension over Iran’s nuclear program came to a head in June 2025, when Israel conducted a major operation against Iran targeting its nuclear facilities, military sites, and regime infrastructure. The United States also joined the 2025 conflict, and Israel and the United States again launched strikes against Iran in February 2026.

Who are the key figures involved?

Some of the most important people and institutions in the negotiations that began in early 2025:

Other notable figures who were previously involved in negotiations include:

  • Barack Obama: Former president of the United States (2009–17) who oversaw the conclusion of the JCPOA in 2015
  • Hassan Rouhani: Former president of Iran (2013–21) and former nuclear negotiator (2003–05) who oversaw the conclusion of the JCPOA in 2015
  • John Kerry: U.S. secretary of state (2013–17) who led the negotiations with Iran that led to the JCPOA
  • Mahmoud Ahmadinejad: Former president of Iran (2005–13) known for his hard-line stance on Iran’s nuclear program
  • Saeed Jalili: Ahmadinejad’s unyielding chief nuclear negotiator (2007–13) who came in second in Iran’s presidential election of 2024
  • Ebrahim Raisi: Fierce critic of Rouhani and the JCPOA who became president in 2021, after the United States pulled out of the JCPOA, and served until his sudden death in 2024