1957 - Iran and United States signed a nuclear cooperation
deal and the United States delivers a research reactor to Iran a decade later.
1970 - Iran ratified the Nuclear Nonproliferation Treaty
(NPT), giving it the right to a civilian nuclear program but barring it from
seeking an atomic bomb.
1979 - Iran's Islamic revolution upended its ties to major
powers, turning former ally the United States into its main foe.
1995 - Russia agreed to finish construction of Iran's
planned nuclear power plant at Bushehr, originally started by Germany and
shelved after the revolution.
2003 - The UN nuclear watchdog, the International Atomic
Energy Agency (IAEA), alleged Iran has not complied with NPT after the
revelation it has secretly built a uranium enrichment plant at Natanz and a
heavy water plant for plutonium at Arak.
Both can be used to make fuel for nuclear power but they can
also be used in atomic warheads.
Iran accepted European proposals for more transparency in
its nuclear program including snap IAEA inspections.
2004 - The IAEA said Iran did not provided the transparency
it promised. Iran said it would not suspend uranium enrichment activity.
2005 - Russia offered to supply Iran with fuel for Bushehr
to stop it developing its own fuel by making enriched uranium or plutonium.
IAEA said Iran was not in compliance with agreements and EU
countries halted negotiations.
2006 - Iran resumed work at Natanz, said in April it had enriched
uranium for the first time to about 3.5%, far short of the 90% needed for a
warhead.
World powers the United States, Russia, China, France,
Britain and Germany - later known collectively as the P5+1 offered Iran
incentives to halt enrichment.
The United Nations Security Council imposed sanctions on
Iran over its enrichment.
2009 - Western countries alleged Iran was building another
secret uranium enrichment facility under a mountain at Fordow near Qom.
2010 - Iran started making 20% enriched uranium. The UN
Security Council expanded sanctions including an embargo on major weapons
systems, as the US and EU tighten their own sanctions.
A computer virus - Stuxnet - deployed aimed at paralyzing
the Natanz plant, the start of direct operations against Iranian facilities
that Tehran blames on Israel.
2011 - Bushehr nuclear plant started operations. Iran said
it was using more advanced centrifuges to expand its 20% enrichment program.
2013 - Former nuclear negotiator Hassan Rouhani was elected
Iranian president offering new proposals. He and US President Barack Obama hold
a first call between leaders of the countries since 1979.
Iran-P5+1 talks in Geneva resulted in a Joint Plan of Action
with steps required by both sides including reducing Iran's enriched uranium stockpile,
more IAEA access and some sanctions relief.
2014 - Negotiations on a final deal continued through the
year, with Iran halting uranium enrichment to 20% and work at Arak and getting
access to oil revenue frozen by sanctions.
US allies in the region, Israel and Saudi Arabia, repeatedly
cautioned Washington against a deal, saying Iran could not be trusted and
citing its growing sway in the region.
2015 - Iran and the P5+1 agreed the Joint Comprehensive Plan
of Action (JCPOA) deal that limits Iran's nuclear work, allowing more
inspections and a loosening of sanctions.
2016 - IAEA said Iran had met its commitments under the
JCPOA, leading to UN sanctions tied to the nuclear program being lifted.
However, Iran's long-range ballistic missile tests prompt unease
despite Tehran saying they could not carry nuclear warheads.
2017 - New US President Donald Trump declared the JCPOA was
the "worst deal ever" and unilaterally pulled out. Despite Trump promising
a better deal there have been no new talks.
2018 - The US reimposed on Iran.
2019 - With ties between Iran and the West deteriorating, a
string of attacks on Gulf oil tankers and other regional energy facilities were
blamed by the US on Iran.
2020 - A blast rocks Iran's Natanz plant and a nuclear
scientist is assassinated near Tehran with Iran blaming both incidents on
Israel.
2021 - With Trump out of the White House, the US and Iran
resumed indirect talks but there was little progress.
Iran started enriching uranium to 60% - not too far from 90%
needed for a bomb.
There were attacks on Iran's Natanz and a centrifuge factory
in Karaj.
2022 - The IAEA accused Iran did not answer questions over
uranium traces found at more sites. Iran stopped IAEA inspections and installed
more new centrifuges at Natanz.
2025 - Trump returns to the White House and declared Iran must
agree to a nuclear deal or there will be bombing.