US President Donald Trump denounced Iran as a "fanatical regime" and refused to continue the signing of an international nuclear deal.
In his speech, Friday (13/9) in Washington DC, Trump accused Iran of sponsoring terrorism and proposed new sanctions.
Trump said Iran had breached a 2015 agreement, which imposes restrictions on Iran's nuclear capabilities in return for easing an international embargo.
International observers say Iran has complied with the agreement in full.
However, in his speech at the White House, Trump said he acted to reject Iran's "whole nuclear arsenal".
"We are not going to continue with what might be expected to result in more violence, more terror, and Iran's nuclear threats real," he said.
What does Trump reject?
Congress requires the US president to set every 90 days that Iran holds its deal. Trump has granted two endorsements, but refused to sign the third ahead of the deadline on Sunday.
Congress currently has 60 days to decide whether to withdraw from a nuclear deal by reimposing sanctions.
Agreement signed by Iran and six major countries namely England, US, Russia, France, Germany and China. A number of lawyers involved in the deal fear the United States will completely retreat.
Instead, he basically handed the matter over to Congress, who will now decide whether to write the limits that suit Trump's wishes.
The President made it clear that if there were no changes then he would cancel the deal.
"If we do not get a solution with Congress and our allies, then the deal will be stopped," he said. "It's in the middle of a continuous review and our participation can be canceled by me, as president, anytime."
What changes Trump want?
Trump is seeking to end a nuclear deal, allowing for the lifting of Iran's nuclear enrichment program restrictions after 2025.
He also called for new sanctions for the Iranian Revolutionary Guards' elite forces, which he calls the "corrupt Iranian leader of terror", and a ban on Iran's ballistic missile program, which is not covered by the deal.
Last month, Iran said it had successfully test-fired a new medium-range missile with a range of 2,000 kilometers. Trials can not be verified internationally.
The President said that congressional leaders have drafted an amendment that could reduce the development of ballistic missiles and eliminate expiration dates on restrictions on Iran's nuclear development.
What is the response of the countries involved in the deal?
Iranian President Hassan Rouhani said that the US is "getting isolated" and can not change the nuclear deal.
"As long as our rights are guaranteed, as long as our interests are served, as long as we benefit from a nuclear deal, we will respect and comply with the agreement," Rouhani said.
Yukiya Amano, leader of the International Atomic Energy Agency (IAEA), said Iran is in agreement and is subject to "the world's most powerful nuclear verification regime".
European diplomats warned that any unilateral change to the deal would spark a deadlock in the deal and return to nuclear disputes in the Middle East.
EU foreign policy captain Federica Mogherini called the "strong" agreement and no "violations" were committed by Iran.
He said there was no "presidential elite anywhere in the world" that could stop the deal.
In a joint statement, Britain, Germany and France said they were "concerned" by Trump's move but remained committed to the deal.
After North Korea, Trump is now slamming Iran over the 2015 nuclear deal
The countries said they were "equally concerned about the ballistic program and Iran's regional activities."
Russia says it remains committed to the deal and rejects the use of "aggressive and threatening rhetoric in international relations".
Israeli Prime Minister Benjamin Netanyahu congratulates Trump, whom he calls "boldly facing Iran's terrorist regime". Saudi Arabia also supports the "firm strategy" of the US president.
What has changed?
President Trump has changed the list of threats in the Middle East, with Iran replacing a group calling itself ISIS Islamic State as Enemy Number One.
The view is supported by supporters in the region including Israel and the Arab Gulf leaders who have long viewed Iran as their main threat, and rivals in the Middle East.
They hate Washington's deal with Iran during President Obama's administration. Like President Trump, those countries want to change that decision.
New approach to impose sanctions back but stop accusing the elite Revolutionary Guards as a terrorist group - a move that Iran calls the same as the declaration of war.
The current urgent question is whether this new strategy will spark the spirit of Iranian hardliners including the Revolutionary Guards.
Like US troops, the Revolutionary Guards are also involved to defeat ISIS in Iraq and Syria, and may also be seen as a new enemy.
What is a nuclear deal?
Formally known as the Comprehensive Joint Action Plan, designed to prevent Iran from developing nuclear weapons.
The deal also lifted some sanctions that prohibit Iran from selling oil in international markets.
The lifting of the sanctions depends on restrictions on Iran's nuclear program. The country must reduce its uranium inventory, not build a reactor for 15 years and also allow inspectors to enter the country.
