Tensions between Iran and the US show no sign of de-escalating after Tehran denounced the latest sanctions implemented by Washington.
Iran claim the sanctions, implemented on Monday, mean a "permanent closure" to diplomacy between the two countries as President Hassan Rouhani derided the White House as being "afflicted by mental retardation".
Trump said the new measures were a response to Iran's alleged attack on two oil tankers in the Gulf of Oman, and the shooting down of an American drone over international waters. He tweeted an Iranian attack on any US interest will be met with "great and overwhelming force ... overwhelming will mean obliteration".
So what are the latest developments in this escalating situation, and could it lead to war?
What is the latest development?
The US has slapped fresh sanctions on Iran, designed to increase pressure on its leaders.
The sanctions target Iran's Supreme Leader Ayatollah Ali Khamenei, damaging his ability to access financial resources. Eight Revolutionary Guard commanders were also affected.
After signing the sanctions, Mr Trump said: "These measures represent a strong and proportionate response to Iran's increasingly provocative actions.
"We will continue to increase pressure on Tehran until the regime abandons its dangerous activities and aspirations including the pursuit of nuclear weapons."
Washington said it planned to impose similar sanctions on Iran's foreign minister Mohammad Javad Zarif later this week.
ITV News correspondent John Irvine has given his thoughts on how the sanctions may be interpreted in Iran.
What is Iran's response to the sanctions?
To put it simply, they're not pleased.
Iran claims the sanctions represent a "permanent closure" to diplomacy.
President Hassan Rouhani launched a scathing attack on Donald Trump, claiming he was someone "afflicted by mental retardation".
Writing on Twitter, Mr Mousavi said: “Imposing useless sanctions on Iran’s supreme leader and the commander of Iran’s diplomacy is the permanent closure of the path of diplomacy.
“Trump’s desperate administration is destroying the established international mechanisms for maintaining world peace and security”.
Iran's ambassador to the UN, Majid Takht Ravanchi, said the situation in the region was now "very dangerous" amid escalating sanctions and counter-claims.
Why was an American drone shot down?
Iranian President Hassan Rouhani said Iran expects “international bodies to show proper reaction” to what he called an “invasion move” after Iran’s military shot down a US drone Tehran insists was in Iranian airspace.
The US claims it was flying over international waters and Donald Trump responded by ordering US military cyber forces to target Iranian military computer systems.
President Trump claimed on Twitter that he backed away from plans for a more conventional strike 10 minutes before it was due to take place after learning around 150 Iranians would be killed.
The US military's Central Command (CENTCOM) confirmed the drone was an RQ-4 Global Hawk, saying the downing took place in international airspace and describing it as an "unprovoked attack".
Iran says it chose not to fire on a manned US military aircraft flying in the area at the same time as the downed drone – a decision Trump praised.
Where do the escalating tensions stem from?
In 2015, Iran agreed a long-term deal on its nuclear programme with the US, UK, France, China, Russia and Germany.
Under the accord, Iran agreed to limit its sensitive nuclear activities and allow in international inspectors in return for the lifting of crippling economic sanctions.
It came after years of tension over Iran's alleged efforts to develop a nuclear weapon.
Iran insisted that its nuclear programme was entirely peaceful, but the international community did not believe that.
However, in 2018 Mr Trump pulled the US out of the deal which he called "terrible" and imposed more sanctions on Iran, crippling the country's economy.
What role does uranium play?
The nuclear deal was intended to stop Iran enriching uranium, which although it can be used for nuclear power, can be used to develop nuclear weapons.
After the US pulled out of the nuclear deal and imposed sanctions on Iran, the country did not see the benefits of sticking to it, and hoped to push European powers towards helping the easing of the strict conditions.
Iran's atomic spokesperson Behrouz Kamalvandi suggested that his country's enrichment could reach up to 20%, just a step away from weapons-grade levels.
This would break the 2015 nuclear deal, as Iran had agreed to keep a stockpile of no more than 300kg (660 pounds) of low-enriched uranium.
Mr Kamalvandi said that given Iran’s recent decision to quadruple its production of low-enriched uranium, it would pass the 300kg limit on Thursday, June 27.
What is uranium enrichment?
Enriching a supply of uranium means altering its chemical structure to boost its concentration.
Depending on how much uranium is enriched, it can be used to fuel nuclear reactors, or can be turned into chemical weapons.
Iran maintains its nuclear programme is for peaceful purposes.
What should we make of the US deployment of extra troops?
Acting Defence Secretary Patrick Shanahan announced on Monday that the US would be increasing its military presence in the region, following the attacks on the tankers which the US blamed on Iran.
An additional 1,000 troops would be deployed to "ensure the safety and welfare of our military personnel working throughout the region to protect our national interests", Mr Shanahan said.
No further details were given on where the additional troops would be deployed.
Monday's announcement comes after President Donald Trump announced an extra 1,500 would be sent last month.
Mr Shanahan and Secretary of State Mike Pompeo have reiterated that the US has no desire to go to war, as has Iran.
So, has the oil tanker attack heightened tensions?
The US claims Iran planted mines on two oil tankers last week in the Gulf of Oman - something Tehran denies.
The US has released images which it claims prove Iran was behind the attack.
The images, many taken from a US Navy helicopter, show what the Pentagon said were Iranian forces removing an unexploded mine from the side of the Japanese-owned Kokuka Courageous oil tanker in the Gulf of Oman.
Officials last week said the move appeared to be an attempt to remove forensic evidence from the scene of the attack, but it is not clear if examination of the mine would have made it definitively clear that the device was planted by the Revolutionary Guard.
Tehran has repeatedly threatened to close the vital Strait of Hormuz, through which 20% of the world’s oil flows.
What impact has increased tensions had on Iran?
It's not good for Iran.
Following the US's withdrawal from the nuclear agreement in 2015, America began ramping up sanctions on Tehran.
Other countries which deal with Iran are also being penalised, leading to other nations turning their back on Tehran.
Iran's economy, which relies heavily on oil, has been crippled as a result.
Supporters of the regime say Iran's increased nuclear activity is a reaction to the outside influences put on its economy by the US.
Iranian President Hassan Rouhani said America's "hostility directly targets every single Iranian", and admitted the "low income and weak classes of the society are undergoing more pressure compared to other classes".
He added: "Iran has been loyal to its commitments, to its signature and international agreements.
"The one who is standing up to us today [referring to US president Donald Trump] has stomped on promises, agreements and international regulations."
A report by the World Bank found Iran's economy continued to slow down in the first quarter of 2018/19 as the US sanctions were reimposed.
What has the reaction been from across the world?
Europe's main players, including the UK, France and Germany, have been scrambling to save what is left of the nuclear deal.
Mr Rouhani has said it can still be saved, if they are able to help Iran's economy.
Britain, France and Germany have tried to set up a special mechanism, known as Instex, to allow European firms to trade with Iran.
However European firms are reluctant to commit to any deals which could see sanctions imposed on them by the US.
Meanwhile China has urged both the US and Iran to scale back tensions.
Foreign minister Wang Yi warned of opening a "Pandora's box" in the Middle East.
China is the world's largest buyer of Iranian oil and has maintained its support for the Iran nuclear deal.