The news comes after the Islamic Republic launched a night strike on US-backed militias in Syria claiming it was punishing its enemy’s “wickedness”.
The US is taking a stand against Iran as a 12-mile stretch of the Iraq-Syria border becomes the focal point of a drawn-out struggle between Iran and the US for dominance in the Middle East.
Some officials are concerned the military posturing could lead to full-scale chaos like that seen in the aftermath of the 2003 invasion of Iraq when Iran-sponsored soldiers killed scores of US and British troops.
Iranian-backed militia has commandeered the dangerous territory on the Iraqi side of the border in an audacious display of sabre-rattling across the besieged zone.
A military base, containing thousands of Shia fighters loyal to Tehran, resides just over the frontier in Syria, according to analysts.
The presence of the Shia fighters has prompted US President Donald Trump to think again about pulling out of the region once ISIS is defeated.
Speaking to the Times, a US diplomat in the region said: “Trump was opposed to staying put in Syria but it seems what they are calling the ‘steady state’ has got its way.
“There doesn’t seem any likelihood of troops pulling out soon.”
Iran has sent foreboding threats to the US in response – thrusting yet more uncertainty on the already beleaguered region.
Satellite imagery by an Israel-based company shows what is believed to be a military base belonging to Iran-backed fighters – on the Syrian side.
The base could contain up to 8,000 fighters from Iraq, Afghanistan, and other Middle Eastern countries.
Officials from the Trump administration contend Iran is harbouring a “Shia crescent” from Tehran to the Mediterranean.
Trump’s isolationist policy in the region has shifted as his chief officials – such as national security adviser, John Bolton, and secretary of state Mike Pompeo – insist the approach is incompatible with the US desire to confront Iran and thwart its expansion ambitions.
Iran has responded furiously to the change in policy.
General Qassem Soleimani, head of the Iranian Revolutionary Guard’s foreign legion, al-Quds Force, said in the summer: “We are near you, where you can’t even imagine.
“If you begin the war, we will end the war.
“You know that this war will destroy all that you possess.”