President Donald Trump had given the go-ahead for a wave of retaliatory strikes against Iran yesterday before opting to cancel the attack, according to reports.
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Trump had planned strikes against a “handful” of targets, according to the New York Times, but cancelled the operation in its early stages.
The White House has not yet responded.
The attacks would have seen the US retaliate after Iran shot down a US drone earlier this week.
Iran said the drone entered Iranian airspace early yesterday morning, but the US said the drone was in international airspace.
As late as 7pm in Washington (11pm BST), White House officials were still expecting strikes on a set of Iranian targets such as radar and missile batteries, according to the New York Times.
But “word came to stand down” as planes were in the air and ships in position, the publication reported.
The strikes were due to take place just before dawn this morning to minimise risks to Iranian military or civilians.
The Pentagon recommended strikes, according to the Associated Press.
But Trump cancelled the operations after discussions with national security advisers and congressional leaders.
Senate Democrat Chuck Schumer said: “The President may not intend to go to war here, but we’re worried that he and the administration may bumble into a war.”
US Secretary of State Mike Pompeo and national security adviser John Bolton had urged Trump to take a tough response but others pressed for a more careful response.
Tensions are escalating between the two countries.
Trump pulled the US out of a 2015 nuclear agreement designed to limit Iran’s nuclear ambitions.
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Iran has subsequently announced that it is set to exceed international agreed limits on its nuclear programme.
Meanwhile the US recently pointed the finger at Iran for attacks on two oil tankers.