A look at the long, fraught timeline of Iran nuclear tensions as talks with US loom

Iran and the United States are due to hold new talks in Geneva on Thursday over Tehran's nuclear program.

The talks come as America has assembled the largest fleet of warplanes and aircraft in the Mideast in decades as part of President Donald Trump's efforts to force Iran into a deal after it saw nationwide protests against its theocracy.

Here's a timeline of the tensions over Iran's atomic program:

Early days

1967 — Iran takes possession of the Tehran Research Reactor supplied by America under the ''Atoms for Peace'' program.

1979 — U.S. ally Shah Mohammad Reza Pahlavi, fatally ill, flees Iran as popular protests against him surge. Ayatollah Ruhollah Khomeini returns to Tehran and the Islamic Revolution sweeps him to power. Students seize the United States Embassy in Tehran, beginning the 444-day hostage crisis. Iran's nuclear program goes fallow under international pressure.

August 2002 — Western intelligence services and an Iranian opposition group reveal Iran's secret Natanz nuclear enrichment facility.

October 2003 — Iran suspends uranium enrichment under international pressure.

February 2006 — Iran announces it will restart uranium enrichment following the election of hard-line president Mahmoud Ahmadinejad. Britain, France and Germany walk out of stalled negotiations.

June 2009 — Iran's disputed presidential election sees Ahmadinejad reelected despite fraud allegations, sparking protests known as the Green Movement and a violent government crackdown.

October 2009 — Under U.S. President Barack Obama, the U.S. and Iran open a secret back-channel for messages in the sultanate of Oman.

July 2012 — U.S. and Iranian officials hold secret face-to-face talks in Oman.

The nuclear deal collapses

May 8, 2018 — Trump unilaterally withdraws the U.S. from the nuclear agreement, calling it the ''worst deal ever.'' He says he'll get better terms in new negotiations to stop Iran's missile development and support for regional militias. Those talks don't happen in his first term.

May 8, 2019 — Iran announces it will begin backing away from the accord. A series of regional attacks on land and at sea blamed on Tehran follow.

Jan. 3, 2020 — A U.S. drone strike in Baghdad kills Gen. Qassem Soleimani, the architect of Tehran's proxy wars in the Middle East.

Jan. 8, 2020 — In retaliation for Soleimani's killing, Iran launches a barrage of missiles at military bases in Iraq that are home to thousands of American and Iraqi troops. More than 100 U.S. service members suffer traumatic brain injuries, according to the Pentagon. As Iran braces for a counterattack, the Revolutionary Guard shoots down a Ukrainian passenger plane shortly after takeoff from Tehran's international airport, reportedly mistaking it for a U.S. cruise missile. All 176 people on board are killed.

April 6, 2021 — Iran and the U.S. under President Joe Biden begin indirect negotiations in Vienna over how to restore the nuclear deal. Those talks, and others between Tehran and European nations, fail to reach any agreement.

April 11, 2021 — A second attack within a year targets Iran's Natanz nuclear site, again likely carried out by Israel.

April 16, 2021 — Iran begins enriching uranium up to 60% — its highest purity ever and a technical step from weapons-grade levels of 90%.

Feb. 24, 2022 — Russia launches its full-scale invasion of Ukraine. Moscow ultimately will come to rely on Iranian bomb-carrying drones in the conflict, as well as missiles.

July 17, 2022 — An adviser to Iran's supreme leader, Kamal Kharrazi, says Iran is technically capable of making a nuclear bomb, but has not decided whether to build one.

Oct. 7, 2023 — Hamas militants from the Gaza Strip storm into Israel, killing around 1,200 people and taking 251 others hostage, beginning the most intense war ever between Israel and Hamas. Iran, which has armed Hamas, offers support to the militants. Regional tensions spike.

Nov. 19, 2023 — Yemen's Houthi rebels, long supported by Iran, seize the ship Galaxy Leader, beginning a monthslong campaign of attacks on shipping through the Red Sea corridor that the U.S. Navy describes as the most intense combat it has seen since World War II. The attacks mirror tactics earlier used by Iran.

April 14, 2024 — Iran launches an unprecedented direct attack on Israel, firing over 300 missiles and attack drones. Israel, working with a U.S.-led international coalition, intercepts much of the incoming fire.

April 19, 2024 — A suspected Israeli strike hits an air defense system by an airport in Isfahan, Iran.

July 31, 2024 — Ismail Haniyeh, a Hamas leader, is assassinated during a visit to Tehran after the inauguration of reformist President Masoud Pezeshkian. Israel later takes responsibility for the assassination.

Oct. 1, 2024 — Iran launches its second direct attack on Israel, though a U.S.-led coalition and Israel shoot down most of the missiles.

Oct. 16, 2024 — Israel kills Hamas leader Yahya Sinwar in the Gaza Strip.

Oct. 26, 2024 — Israel openly attacks Iran for the first time, striking air defense systems and sites associated with its missile program.

Trump returns and reaches out

Jan. 20, 2025 — Trump is inaugurated for his second term as president.

March 7, 2025 — Trump says he sent a letter to Khamenei seeking a new nuclear deal with Tehran.

March 15, 2025 — Trump launches intense airstrikes targeting Houthi rebels in Yemen, the last members of Iran's self-described ''Axis of Resistance'' capable of daily attacks.

April 7, 2025 — Trump announces the U.S. and Iran will hold direct talks in Oman. Iran says they'll be indirect talks, but confirms the meeting.

April 12, 2025 — The first round of talks between Iran and the U.S. take place in Oman, ending with a promise to hold more talks after U.S. Mideast envoy Steve Witkoff and Iranian Foreign Minister Abbas Araghchi ''briefly spoke'' together.

April 19, 2025 — The second round of talks between the U.S. and Iran are held in Rome.

May 11, 2025 — Iran and the U.S. meet in Oman for a fourth round of negotiations ahead of Trump's trip to the Mideast.

May 23, 2025 — Iran and the U.S. meet in Rome for a fifth round of talks, with Oman saying the negotiations made "some but not conclusive progress."

The Iran-Israel war begins

June 9, 2025 — Iran signals it won't accept a U.S. proposal over the nuclear program.

June 12, 2025 — The Board of Governors at the International Atomic Energy Agency finds Iran in noncompliance with its nuclear obligations. Iran responds by announcing it has built and will activate a third nuclear enrichment facility.

June 22, 2025 — The U.S. intervenes in the war, attacking three Iranian nuclear sites.

June 23, 2025 — Iran responds to the U.S. attack by targeting a military base in Qatar used by American troops, causing limited damage.

June 24, 2025 — Trump announces a ceasefire in the war.

July 25, 2025 — Iranian and European diplomats hold talks in Istanbul over Iran's nuclear program.

Aug. 8, 2025 — France, Germany and the United Kingdom warn Iran in a letter that it will reimplement U.N. sanctions if there is no ''satisfactory solution'' to the nuclear standoff by Aug. 31.

Sept. 9, 2025 — Iran and the International Atomic Energy Agency reach a deal over potentially starting inspections, but questions remain over its implementation.

Sept. 19, 2025 — U.N. Security Council declines to stop ''snapback'' sanctions on Iran.

Sept. 26, 2025 — U.N. Security Council rejects China and Russia's last-minute effort to stop ''snapback.''

Sept. 28, 2025 — U.N. reimposes ''snapback'' sanctions on Iran barring any last-minute diplomacy.

New protests roil Iran

Jan. 3, 2026: Khamenei says ''rioters must be put in their place,'' in what is seen as a green light for security forces to begin more aggressively putting down the demonstrations.

Jan. 8, 2026: Following a call from Iran's exiled crown prince, a mass of people shout from their windows and take to the streets in nationwide protests. The government responds by blocking the internet and international telephone calls in a bid to cut off the country of 85 million from outside influence. An ensuing security force crackdown kills thousands and sees tens of thousands detained.

Jan. 13, 2026: Trump says he has called off any meetings with the Iranians and promises that unspecified ''help is on its way.''

Jan. 26, 2026: The aircraft carrier USS Abraham Lincoln and three accompanying warships arrive in the Middle East amid Trump's threats to attack.

Feb. 3, 2026: A U.S. Navy fighter jet shoots down an Iranian drone approaching the Lincoln in the Arabian Sea. Iranian fast-attack boats attempt to stop a U.S.-flagged ship in the Strait of Hormuz.

Feb. 17, 2026: Iran and the U.S. hold talks in Geneva while Tehran says it has temporarily closed the Strait of Hormuz, the narrow mouth of the Persian Gulf through which a fifth of all oil traded passes.