(CNN) - The US military is disputing Iran's claims that the American drone shot down Thursday violated Iranian airspace and was engaged in "spying," a key detail that could determine what comes next in the volatile situation playing out between Washington and Tehran.
While Iran's Islamic Revolutionary Guard Corps argues the drone "was over Iranian territory" when it was shot down, a US official told CNN that the unmanned aircraft was in international airspace and was shot down over the Strait of Hormuz, a strategically important waterway that has become a flashpoint for ongoing tensions in the Middle East.
Lt. General Joseph Guastella, Commander of US Air Forces Central Command, called Iran's claim "categorically false," adding that "the aircraft was over the Strait of Hormuz, and fell into international waters."
The Pentagon released a map showing exactly where they say the aircraft was shot down.
Later Thursday, Iranian Foreign Minister Javad Zarif posted what he says are the US drone's coordinates when it was targeted by the IRGC.
"At 00:14 US drone took off from UAE in stealth mode & violated Iranian airspace. It was targeted at 04:05 at the coordinates (25°59'43"N 57°02'25"E) near Kouh-e Mobarak. We've retrieved sections of the US military drone in OUR territorial waters where it was shot down," Zarif tweeted.
So why does it matter if the drone was shot down in international airspace versus over Iranian territory?
By claiming that the US aircraft was not only violating sovereign airspace but engaged in "spying and information gathering," Iran is likely to attempt to legally justify its response as self-defense -- walking the line between sending a message to Washington while limiting the chances of military retaliation.
"The Iranians are clearly trying to demonstrate their ability to defend themselves and to deter further American action. They probably assumed that by targeting a drone, they could send that message at minimal risk," according to CNN military analyst John Kirby, a retired Navy Rear Admiral.
A top Iranian security official seemed to suggest that was the case later Thursday by warning foreign planes against aggression to its airspace.
"Iran will defend all its sea, land and air borders and aggression to its air space is its' redline," Iran's Secretary of Supreme National Security Council, Ali Shamkhani said according to state-run IRNA news reporting.
Yet, the Iranians may have overplayed their hand in this case, according to Kirby, who said shooting the drone down in international airspace "could now give the Trump administration grounds to solicit more support from the international community for any acts of reprisal and weaken European reticence to continue supporting Iran's economy."
According to the Navy's handbook on the Law of Naval Operations, a hostile act is defined as "an attack or other use of force against the United States, US forces, or other designated persons or property; it also includes force used directly to preclude or impede the mission and/or duties of US forces."
"I would think the Trump administration could -- if they choose -- cite the principle of self-defense under the UN Charter and conduct operations accordingly," Kirby said. "But those operations would have to be proportional to the threat -- a threat that has now been made more challenging by the sophistication of Iranian air defenses."
"All airspace within the range of Iranian systems must now be considered contested. Absent a major escalation by the US to suppress Iranian air defenses, this will certainly constrain American military options," he added.
Strategic importance of Strait of Hormuz
The Pentagon's claim that the US drone was shot down over the Strait of Hormuz is also a significant detail in the broader context of escalating tensions in the region involving Iran.
There is no place in the world more important for the global supply of oil than the Strait of Hormuz and the US has vowed to never allow Iran to prevent open passage through the waterway.
The channel, which is only 21 miles wide at its narrowest point, is the only way to move oil from the Persian Gulf to the world's oceans. And that's why the attack early Thursday on two ships — one carrying oil and the other transporting a cargo of chemicals — in the nearby Gulf of Oman is such a concern.
If the Strait were to be closed because of the threat of ongoing attacks, it would be a massive blow to the world's economy. Oil prices, which had been falling recently, jumped 4% on news of Thursday's attack.
The Strait of Hormuz, which links the Gulf of Oman and the Persian Gulf, "is the world's most important choke point," said the US Energy Information Administration.
President Donald Trump left the door open for a possible military strike against Iran in response to the downing of an American drone in an ominous fashion on Thursday morning by tweeting "Iran made a very big mistake!"
However, Trump followed up that tweet by saying he believes Iran mistakenly shot down the US drone and finds it "hard to believe it was intentional."
"Probably Iran made a mistake. I would imagine it was a general or somebody who made a mistake in shooting that drone down," he told reporters in the Oval Office.
Still, there is also a strong suspicion among many analysts that outspoken Iran hawks, like Republican senators Tom Cotton of Arkansas and Lindsey Graham of South Carolina, are trying to maneuver Trump into a position where a military confrontation becomes inevitable without an Iranian capitulation that seems highly unlikely.
And it remains to be seen how the Trump administration will react.
"I do not expect this latest incident to, by itself, lead to outright conflict. But it is certainly escalatory and, regrettably, may be further limiting the already small decision space Trump had given himself," Kirby said.
CNN's Ryan Browne, Stephen Collinson and Frederik Pleitgen contirbuted to this report.
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