The US miliary confirmed the Iranians had shot down a RQ-4A drone similar to the one pictured © Northrop Grumman

President Donald Trump played down the significance of Iran shooting down a US drone over the Gulf, saying he found it “hard to believe” the move was intentional only hours after he had warned that Tehran had made a “very big mistake”.

Tensions between the US and Iran, which were already high, mounted on Thursday after Iran shot down a US Navy surveillance drone. The Iranian Revolutionary Guard said its air force fired on the drone after it “violated” Iranian airspace, but the US said the unmanned surveillance aircraft was flying in international airspace.

“I find it hard to believe it was intentional,” Mr Trump said on Thursday while receiving Justin Trudeau, Canadian prime minister, at the White House. “It could have been somebody who was loose and stupid that did it . . . But it was a very foolish move.”

Coming one week after Washington accused Iran of attacking two tankers in the Gulf of Oman, the shooting down of the drone raised concerns the US would respond with military action, increasing the possibility of a full-scale conflict in the Middle East.

The White House held a classified briefing for lawmakers on Thursday afternoon. Afterwards, Nancy Pelosi, the Democratic speaker of the House of Representatives, urged the administration to avoid taking a “reckless” approach to the crisis.

“It is essential that we remain fully engaged with our allies, recognise that we are not dealing with a responsible adversary and do everything in our power to de-escalate,” Ms Pelosi said. “This is a dangerous, high-tension situation that requires a strong, smart and strategic, not reckless, approach.”

Chuck Schumer, the top Democrat in the Senate, said he had made clear to Mr Trump that he would need congressional approval for any military action against Iran.

“The president may not intend to go to war here. But we’re worried that he and the administration may bumble into a war,” Mr Schumer said. “One of the best ways to avoid bumbling into war . . . is to have a robust open debate and for Congress to have a real say. We learnt that lesson in the run-up to Iraq.”

Some critics are worried John Bolton, the hawkish national security adviser, will urge Mr Trump to take military action against Iran. Asked on Thursday if some of his team were trying to push him into war, Mr Trump said that was not the case.

“No, not at all. Not at all. In fact, in many cases, it’s the opposite,” Mr Trump said. “I said I want to get out of these endless wars. I campaigned on that . . . But this is something, this is a new wrinkle. This is a new fly in the ointment, what happened shooting down the drone. And this country will not stand for it, that I can tell you.”

Tom Wright, a foreign policy expert at the Brookings Institution, said: “Trump has been suspicious of John Bolton manipulating him into a war since he started and that suspicion remains today. He wants to squeeze Iran but seems not to want a war.”

Earlier on Thursday, Lieutenant General Joseph Guastella, the commander of US air forces in the Middle East, said the attack occurred “in the vicinity of established air corridors” and that the drone never flew closer than 34km from the Iranian coast.

US Central Command, which overseas US military operations in the region, said its Global Hawk high-altitude surveillance drone — which can remain airborne for more than 24 hours — was shot down by an Iranian surface-to-air missile while over the Strait of Hormuz, one of the world’s most important shipping routes for oil and gas.

The Iranian Revolutionary Guard said the aircraft was shot down in the southern Iranian province of Hormuzgan, adjacent to the Strait of Hormuz.

When asked how he would respond, Mr Trump said in the Oval Office: “You’ll find out.

“This drone was in international waters, clearly,” the president said. “We have it all documented scientifically, not just words. And they made a very bad mistake.”

The Pentagon released a map that it said showed the drone’s path from launch to where it was shot down, in an effort to prove it had not entered Iranian airspace. 

The attack sent oil prices sharply higher, with Brent crude trading near its highest levels of the month. The international benchmark was up 4.5 per cent at $64.62 a barrel. 

An image released by IRNA, Iran's official news agency, puporting to show the US drone after it was hit © IRNA

Iran criticised the US for what it said was a provocative action. General Hossein Salami, commander of the Revolutionary Guard, told Iranian state television that the downing of the drone “sent a clear message” to the US. 

Mohammad Javad Zarif, Iran’s foreign minister, wrote on Twitter that Iran would take the case of the US encroaching on Iranian territory to the UN. “We don’t seek war, but will zealously defend our skies, land and waters,” Mr Zarif wrote. 

The incident comes just days after Washington said it would send 1,000 more troops to the Middle East. The deployment followed attacks on two oil tankers in the Gulf of Oman, east of the Hormuz strait, last week, which the US and Saudi Arabia have blamed on Iran. Iran has denied any involvement.

Shortly after Washington blamed Iran for the attacks, Tehran announced it would break the limits on its enriched uranium stockpile agreed in the 2015 nuclear agreement. 

Timeline: Rising tensions in the Gulf

May 6

John Bolton, US national security adviser, announces that the Trump administration is deploying an aircraft-carrier strike group and bombers to the Middle East in response to troubling “indications and warnings” from Iran.

May 12

Four tankers, including two Saudi vessels, are hit by “sabotage” attacks in the Gulf of Oman off the coast of Fujairah, one of the seven emirates of the United Arab Emirates. There were no casualties or oil spills but the vessels were damaged. US officials said they suspected Iran. Tehran denied any involvement. 

May 14

Two Saudi Arabian oil pumping stations along a pipeline to the Red Sea port of Yanbu are hit by drone attacks. The attacks are claimed by Yemen’s Houthi rebels. The US and Saudi Arabia accuse Iran of smuggling weapons to the Houthis. 

May 16

Saudi Arabia launches air strikes on Yemen’s capital in retaliation against the Houthis.

June 12

Houthi rebels fire a rocket at Abha International Airport in southern Saudi Arabia, wounding at least 26 civilians. 

June 13

Two oil tankers, the Norwegian-owned Front Altair and the Japanese-owned Kokuka Courageous, are attacked in the Gulf of Oman.

June 17

Iran announces that it will breach its uranium enrichment limits within 10 days, threatening a collapse of the 2015 nuclear deal. Hours later, US President Donald Trump said an additional 1,000 American troops would be deployed to the Middle East.

June 20

Iran’s Revolutionary Guard says it has shot down a US drone.

Additional reporting by Andrew England in London and Siddarth Shrikanth in Hong Kong

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