Tensions between the United States and Iran could be rising to "the brink of a catastrophic military clash", experts have warned, after the US announced plans to send more troops to the Middle East and oil prices looked set to rise.

Key points: Iran is threatening to break a uranium stockpile limit set in a 2015 nuclear deal

Iran is threatening to break a uranium stockpile limit set in a 2015 nuclear deal The US has already evacuated "non-emergency employees" from Iraq

The US has already evacuated "non-emergency employees" from Iraq Last weeks ship attacks are expected to drive up oil prices and shipping insurance costs

Last week, the US blamed Iran for attacks on two oil tankers, leading Saudi Arabia's Crown Prince Mohammed bin Salman to call on the international community to take a "decisive stand" against Iran.

But many questioned the US accusations — including Japan, who owned one of the two attacked ships — while Iran, who denied any involvement in the attacks, is now threatening to break the uranium stockpile limit set by world powers in a 2015 nuclear deal in the next 10 days.

The landmark 2015 accord has steadily unravelled since the Trump administration pulled out of the deal last year and reimposed tough economic sanctions on Iran, sending the nation's economy into freefall.

"The Trump administration's maximum pressure campaign has led to a climate that is ripe for inadvertent conflict," Ali Vaez, Iran project director for International Crisis Group, told the ABC.

"Each cycle of escalation brings the parties closer to the brink of a catastrophic military clash."

On Thursday, Iran shot down a US military drone claiming it had entered Iranian territory, which the US countered as being shot down in international airspace.

The current situation marks the latest in a series of clashes between the US and Iran, and if tensions continue to escalate, experts warn that oil prices could dramatically rise as multiple countries — including Australia — could be drawn into a conflict that could wreak havoc across an already war-torn Middle East.

Here's what we know so far about the growing, who's involved, and what might happen in coming weeks.

'Absent hard proof': What we know about the latest attacks

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 29 seconds 29 s The US released this video of an alleged Iranian military crew removing mines

The two oil tankers were attacked late last week on Thursday morning, some 40 kilometres off the coast of Iran.

Twenty-three crew members were rescued from the Norwegian-owned Front Altair oil tanker after parts of the ship burst into flames for reasons that are still unknown. Shortly after, 21 Japanese crew members were rescued by the US Navy from the Kokuka Courageous after explosions rocked the ship, yet no-one seems to be able to agree on the origins of the alleged attacks.

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The US military said black-and-white footage filmed from a US aircraft showed Iran's Guards on a patrol boat removing an unexploded mine from the Japanese ship's hull after the crew were evacuated.

But the president of the Kokuka Sangyo shipping company Yutaka Katada, called the US allegations into question, saying crew members had witnessed a "flying object" suggesting the boat was hit by missiles, not a mine.

Analysts told the ABC that none of the evidence seems to be conclusive yet.

"Iran might have the motivation to conduct such attacks, but absent hard proof, it is hard to rule out that it wasn't the act of a spoiler who wanted to make sure that Iran and the US remain on a collision course amid Japanese efforts to de-escalate tensions," Mr Vaez told the ABC.

The US also recently blamed Iran for attacks against four other ships last month, as well as a drone attack on a Saudi Arabian pipeline and a rocket attack near the US embassy in Baghdad — Iran denied involvement in any of the attacks.

This week, European diplomats urged restraint in directing blame without evidence, while United Nations secretary-general Antonio Guterres called for an independent investigation, saying the world could not afford a major confrontation in the Gulf.

A US Central Command photograph showing what it said was damage to the side of the Kokuka Courageous and a probable unexploded limpet mine on the ship's hull. ( Supplied: US Central Command )

'Never threaten the US': Tensions could reignite proxy war

Tensions have been rising between the US and Iran for a while now.

Early last month, the US began deploying additional forces to the region, including an aircraft carrier, B-52 bombers, Patriot missiles and 1,500 troops in response to "troubling indications and warnings" from Iran — this week, Defence Secretary Patrick Shanahan announced an additional 1,000 US troops will be deployed.

Meanwhile, threats have been rife between the two feuding leaders with Mr Trump threatening via Twitter that a fight with the US would be "the official end of Iran", while Iran's President Hassan Rouhani told Mr Trump not to "play with the lion's tail".

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Mr Vaez said the "tit for tat" between Iran and the US could quickly turn into a regional conflagration.

Iran could "activate it's network of proxies and partners" in the region from Yemen to Lebanon, Syria and Iraq to "go after US assets and those of America's allies," he said.

The leader of Lebanon's Hezbollah's warned the United States that if they strike Iran "the entire region will burn", and "all US forces and interests in the region would be annihilated" — the US has already evacuated "non-emergency employees" from Iraq.

Meanwhile, US-ally Saudi Arabia encouraged Washington to cut Iran down to size, and while Riyadh has maintained that they would not be in favour of war, Foreign Affairs Minister Adel al-Jubeir said the kingdom "will defend itself, its citizens and its interests".

Israel, who have advocated for strikes on Iran in the past, have so far kept a distance from the current stand off.

Situation will not 'blow over': How likely is a US-Iran conflict?

The commander of Iran's elite Revolutionary Guards warned the build up of US troops in the region could lead to a "full-scale confrontation". ( AP: Ebrahim Noroozi )

Mr Vaez says a US offer of sanctions relief in return for full compliance with the nuclear deal could defuse the situation, but the biggest risk is "miscalculation".

"Tensions are running high across numerous flashpoints and there are no channels of communication between the two sides."

Alternatively, the remaining parties to the nuclear deal — Europe, China and Russia — can provide Iran with an "economic lifeline" that could help it keep its economy afloat and justify remaining in the deal.

"Donald Trump campaigned on drawing down from the Middle East, and Iran does not have the capability to counter the US in a large-scale conflict," Bryce Wakefield, executive director of the Australian Institute of International Affairs, told the ABC.

"America's decision to augment its troops in the region, however, would suggest that this situation will not just 'blow over' after some heavy posturing."

Dr Wakefield said the possibility of US allies acting as a broker between Washington and Tehran has been hampered by Mr Trump's policy "predicated on ratcheting up tension" in the Middle East.

"The Iranian regime, meanwhile, won't back down amid American demands to dismantle its missile program or end its support for insurgencies elsewhere in the Middle East."

However, Dr Wakefield added that he believes the situation has a long way to go before open conflict breaks out.

If a conflict did break out, what would it mean for Australia?



Last week's oil tanker attacks have already prompted fears of soaring oil prices, and shipping companies are bracing for a rise in insurance costs.

"Australians could be facing higher prices at the pump if the tension carries on," Dr Wakefield warned.

Two oil tanker owners, DHT Holdings and Heidmar, have already suspended new bookings for the Persian Gulf, industry media reported.

"A fifth of the world's oil passes through the Straits of Hormuz. Any instability in the region will mean the world's oil prices will go up," Dr Wakefield said.

But a new US war could mean more than just higher petrol prices.

"In the still fairly distant event of a sustained conflict, the United States would be looking to enlist its allies in action against Iran," Dr Wakefield said, adding that Australia has "a doctrine of support for the United States in combat far beyond Australian shores".

Meanwhile back in the US, Dr Wakefield said a conflict could actually consolidate support for Mr Trump ahead of the 2020 presidential elections.

"People tend to rally around the flag during a conflict," he said.

"However, large sections of the United States oppose Trump vehemently, and they might be highly sceptical of any reasons he gave to go to war."