Donald Trump has stopped short of escalating the worsening standoff with Iran in the Persian Gulf, suggesting that the shooting down of a US drone could have been carried out by a "loose and stupid" Iranian officer without authorisation from Tehran, and emphasising that the aircraft was unmanned.
After meeting with his top national security officials to discuss Wednesday night's downing of a Global Hawk spy drone, the president declared: "I would imagine it was a general or somebody that made a mistake in shooting that drone down.
"I find it hard to believe it was intentional if you want to know the truth. I think it could have been somebody who was loose and stupid that did it," Trump told journalists. "It was a very foolish move."
Trump reinforced the administration's red line that it would respond militarily if Iranian forces or proxies harm Americans - but stressed that was not the case on this occasion.
"We didn't have a man or woman in the drone. It would have made a big, big difference," Trump said. Asked how the US would respond, he said: "You'll find out."
Late on Thursday, the New York Times said Trump had initially approved attacks on a handful of Iranian targets, including radar and missile batteries, before pulling back. Citing officials, the paper said the operation was in its early stages and planes were in the air before it was called off.
Later, Iran's foreign minister and the US military offered competing graphics showing the drone's flight path and where it was brought down.
Javad Zarif said Iran had recovered parts of the drone in its waters and that it had originally taken off from the United Arab Emirates.
A map issued by US Central Command suggested the drone was brought down in international waters in the Strait of Hormuz.
On Thursday night, Democratic congressional leaders urged Trump to work with US allies. House speaker Nancy Pelosi said the administration should "do everything in our power to de-escalate", while Senate Democratic leader Chuck Schumer said he worried the administration "may bumble into a war". He said he told the president during a classified briefing there must be a "robust, open debate" and Congress should have a real say. Adam Schiff, the chairman of the House intelligence committee, said: "The president certainly listened to what we had to say."
Republican Senate majority leader Mitch McConnell, said: "The administration is engaged in what I called measured responses."
Political support for the administration's Middle East policies is shaky. On Thursday, the Senate voted against the White House's use of an emergency declaration to sell $8bn to its allies in the Gulf without congressional approval. His critics are unlikely to muster enough senators to overturn the expected presidential veto, but Thursday's vote was a measure of unease over Trump's close relationship with the Saudi monarchy.
Trump said he was sticking to his promise to extract the US from wars in the Middle East, adding: "But this is a new wrinkle, a new fly in the ointment what happened, shooting down a drone. And this country will not stand for it, that I can tell you."
Iranian officials have said that the shooting down was a deliberate act and a success of the country's security forces, but claimed that the aircraft was over Iranian territory.
The Iranian ambassador to the UN, Majid Takht-Ravanchi, claimed the aircraft was "in stealth mode as it had turned off its identification equipment and engaged in a clear spying operation".
"When the aircraft was returning towards the western parts of the region near the strait of Hormuz, despite repeated radio warnings, it entered into the Iranian airspace," Ravanchi said in a letter to UN secretary general, António Guterres.
"The downing of the American drone was a clear message to America … our borders are Iran's red line and we will react strongly against any aggression … Iran is not seeking war with any country, but we are fully prepared to defend Iran," the IRGC commander, Hossein Salami, said, according to Iranian media.
Trump insisted that the Global Hawk drone was over international waters, saying: "We have it all documented scientifically, not just words."
The US military said the use of a high-powered anti-aircraft missile against a target in international airspace was a danger to commercial airliners in the region.
"This was an unprovoked attack on a US surveillance asset that had not violated Iranian airspace at any time during its mission," Gen Joseph Guastella, US Central Command's top air force commander, told reporters.
"This attack is an attempt to disrupt our ability to monitor the area following recent threats to international shipping and the free flow of commerce," Guastella said. "The aircraft was over the strait of Hormuz and fell into international waters."
US officials confirmed the downed aircraft was a US navy Global Hawk surveillance drone, which had been hit by an Iranian surface-to-air missile over the strait of Hormuz at 11.35pm GMT.
The $130m (£102m) Global Hawk is the world's largest surveillance drone, packed with sophisticated electronics and the size of a small commercial airliner. Iranian forces and allied militias had previously fired at and brought down US Reaper drones, but this is the biggest US target Iran has hit to date, as tensions in the region escalate.
Close to the same time as the drone was shot down, Houthi rebels in Yemen, who are backed by Iran, hit a Saudi desalination plant with an apparently sophisticated missile, and there have been a string of rocket and mortar attacks on or close to US facilities in Iraq.
On Wednesday the Pentagon confirmed it was sending an additional 1,000 troops to the Gulf in response to two attacks on commercial tankers on 13 June which the US has blamed on Iran's IRGC.
Trump downplayed the tanker attacks as "very minor" but US officials have made clear to Iran that it would view an attack on its forces by Iran or proxy militias as a threshold for a military response.
Iran said the US drone was shot down by the "3rd Khordad" air defence system, which is an Iranian equivalent to the Russian Buk system that downed Malaysia Airlines flight MH17 over Ukraine in 2014. The use of such weapons in an area of crowded skies has underlined the dangers of the standoff in the Gulf spinning out of control.
The secretary of Iran's supreme national security council, Ali Shamkhani, had said on Wednesday that Tehran would respond to any intrusion into its airspace or waters.
Shamkhani emphasised that Iran robustly protects its aerial and maritime borders, describing its airspace as the country's "red line". "No matter whose plane trespasses into it, we have always given and will give a harsh response to intruders."
Speaking in London, the Saudi foreign minister, Adel al-Jubeir, said: "The international community is determined to push back against Iran's aggressive behaviour."
Saying steps were being prepared to protect shipping in the Gulf, he added: "Freedom of navigation is essential to global security and the world economy. Any attempt to close the strait of Hormuz will provoke a very strong reaction."