The 2015 nuclear deal raised hopes that Iran might act in a more moderate fashion. But many of Iran's more provocative moves, including ballistic missile tests, aren't subject to the agreement.
Critics say inspectors from the International Atomic Energy Agency are failing to routinely inspect military sites where potential nuclear fuel could be diverted to a covert nuclear weapons program.
President Rouhani's re-election bid has hit a steep challenge from hard-liner Ebrahim Raisi. Though Ayatollah Khamenei will remain supreme leader, the choice still marks a crossroads. Here's a primer.
Secretary of State Rex Tillerson tells Congress that the Trump administration will take another look at sanctions to see if lifting them was in line with U.S. national security interests.
Since the 2015 international agreement to curb Iran's nuclear capabilities in exchange for lifting some sanctions, the U.S. and Iran have argued over what exactly it says about ballistic missiles.
If Trump keeps his promise to do away with the Iran deal, it won't be the first time a Republican administration drops an arms deal inked by Democrats. Something similar happened under George W. Bush.
Iranian leader Hassan Rouhani was at the United Nations this week encouraging the world to work with Iran. But two British men were also there, appealing for the release of relatives held in Iran.
State Department spokesman John Kirby said there was no quid pro quo with the $400 million payment, which he said was tied to a claim Iran launched in an international tribunal.