US forces shot down an Iranian drone on Tuesday in another sign of the mounting tensions between the two nations.
The drone was being piloted towards the USS Abraham Lincoln, an aircraft carrier that has been stationed around the Arabian Sea and the Gulf since last week, according to the US Central Command (Centcom).
Captain Tim Hawkins, a Centcom spokesman, said the Shahed-139 drone "aggressively approached" the ship with "unclear intent... despite de-escalatory measures taken by US forces operating in international waters".
It was subsequently shot down by an F-35C fighter around 500 miles from the Islamic Republic's southern coast.
Just hours later, the US confirmed that Iranian vessels had also attempted to seize an American-flagged oil tanker, the Stena Imperative.
Two smaller boats and a Mohajer drone approached the tanker "at high speeds and threatened to board and seize" it.
The USS McFaul responded and proceeded to escort the Stena Imperative through the region "with defensive air support from the US Air Force," added Centcom.
The escalation in tensions comes ahead of planned negotiations between the two sides, set for Friday, aimed at averting a military clash.
Iran's nuclear enrichment, ballistic missile programme and support for regional proxies - including Hamas and Hezbollah - are understood to be the key issues on the table.
The talks, led by US Middle East Envoy Steve Witkoff and President Trump’s son-in-law Jared Kushner, are expected to take place in Turkey.
The global nuclear watchdog, the IAEA, estimates that Iran possesses around 400kg of 60 per cent enriched material - just a technical step away from the 90 per cent threshold to be considered weapons-grade.
Iran has previously signalled it is willing to negotiate on the level of enrichment, but has ruled out the US demand for a total end to the practice, claiming it is vital for civilian energy projects.
There also appears to be little room for compromise on the demand for strict limitations on its development of ballistic missiles, an arsenal which Tehran insists is an essential and legitimate part of its defence, but Washington and Jerusalem claim fuels Iran's regional aggression.
The US is yet to officially comment on its participation, but President Trump has warned that "bad things" will happen if a deal is not reached.
"We have ships heading to Iran right now, big ones - the biggest and the best - and we have talks going on with Iran, and we’ll see how it all works out," he told reporters in the Oval Office on Monday, referring to his previous threat of an "armada" in the Gulf.
"If we can work something out, that would be great and if we can’t, probably bad things would happen.
“I’d like to see a deal negotiated. I don’t know that that’s going to happen."
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