The United States and Iran on Friday were trying to reach a diplomatic solution to disputes between them that have led to heightened tensions in the Middle East, and warnings from President Donald Trump that military options are at his disposal.

As the U.S. wants talks to include Iran's nuclear ambitions, ballistic missiles, support for terrorist proxies and treatment of the anti-regime protesters, Tehran has insisted on focusing exclusively on its disputed nuclear program and is seeking recognition of its right to enrich uranium.

Here are key moments in relations between Trump's administrations and Iran over recent years:

May 2018: U.S. quits nuclear deal

During his first term, Trump pulled the United States out of a 2015 nuclear agreement known as the Joint Comprehensive Plan of Action, the signature foreign policy achievement of former President Barack Obama.

The deal eased sanctions on Iran in exchange for Tehran limiting its nuclear program to prevent it from being able to make an atomic bomb. Iran denies seeking nuclear weapons.

January 2020: Soleimani killed in strike ordered by Trump

General Qassem Soleimani, the commander of the Quds Force, the overseas arm of the elite Islamic Revolutionary Guard Corps, was killed in Iraq in a drone strike ordered by Trump.

Days after the assassination, the U.S. described the killing as self-defense. The Attorney General at the time, William Barr, said Trump clearly had the authority to kill Soleimani and the general was a "legitimate military target."

A U.N. human rights investigator said the incident was a violation of international law. The Iranian authorities have previously called for Trump to be tried and judged.

August 2020: U.S. attempts 'snapback' of U.N. sanctions on Iran

The U.S. triggered a process aimed at restoring all U.N. sanctions on Iran in August 2020 after the U.N. Security Council rejected a U.S. bid to extend a conventional arms embargo on the country.

The U.S. effort failed after 13 of the 15 Security Council members at the time said the move was void because it relied on a mechanism agreed under the 2015 nuclear deal that the U.S. had quit in 2018.

November 2024: U.S. charges Iranian man in plot to kill Trump

Iranian Farhad Shakeri was charged in connection with an alleged plot ordered by the IRGC to assassinate Trump, according to the Department of Justice.

Shakeri told law enforcement he did not intend to formulate such a plan within the time frame directed by the IRGC, according to the department.

Iran's foreign ministry said at the time in a statement carried by local media that the claim was a "repulsive" plot by Israel and Iranian opposition outside the country to "complicate matters between America and Iran."

June 2025: U.S. strikes Iran nuclear sites

The U.S. attacked key Iranian nuclear sites, joining Israel in the largest Western military action against the Islamist Republic since its 1979 revolution, which prompted a threat of retaliation.

A day later, Iran launched a missile attack on an American air base in Qatar that caused no injuries, shortly after which the 12-day conflict with Israel ended.

September 2025: Sanctions on Iran snap back

U.N. sanctions on Iran were reimposed in a move spearheaded by Western powers that China and Russia unsuccessfully tried to delay. Britain, France and Germany triggered the return of international sanctions over accusations that Tehran violated the 2015 nuclear deal.

February: Diplomacy continues

Talks between both sides held Friday in Oman were described by Iran's Foreign Minister Abbas Araqchi as having gotten off to a "good start," and are set to continue, although he warned "any dialog requires refraining from threats and pressure."

Iran's leadership remains deeply worried Trump might make good on his threats to strike Iran after a U.S. naval buildup in the region. Trump has said "bad things" will probably happen if a deal cannot be reached.

Despite the talks, the U.S. announced Friday it was sanctioning 15 entities and 14 shadow-fleet vessels connected to illicit trade in Iranian petroleum, petroleum products and petrochemical products.