WASHINGTON, United States (AP) — Tensions are flaring in the Persian Gulf after President Donald Trump said the US is “locked and loaded” to respond to a weekend drone assault on Saudi Arabia’s energy infrastructure that his aides blamed on Iran.

The attack, which halved the kingdom’s oil production and sent crude prices spiking, led Trump to authorise the release of US strategic reserves should they be necessary to stabilise markets.

Trump said the US had reason to believe it knew who was behind the attack his secretary of state had blamed on Iran the previous day and said his government was waiting to consult with the Saudis as to who they believe was behind the attack and “under what terms we would proceed!”

The tweets yesterday followed a National Security Council meeting at the White House and hours after US officials offered what they said was proof that the attack was inconsistent with claims of responsibility by Yemen’s Iran-backed Houthi rebels and instead pointed the finger directly at Tehran.

A US official said all options, including a military response, were on the table but added that no decisions had been made. The official spoke on the condition of anonymity to discuss the internal deliberations.

Iran called the US claims “maximum lies” and threatened American forces in the region. The attack dimmed hopes for potential nuclear talks between Trump and Iranian President Hassan Rouhani at the UN General Assembly this week.

The US government produced satellite photos showing what officials said were at least 19 points of impact at two Saudi energy facilities, including damage at the heart of the kingdom’s crucial oil processing plant at Abqaiq. Officials said the photos show impacts consistent with the attack coming from the direction of Iran or Iraq, rather than from Yemen to the south.

Iraq denied that its territory was used for an attack on the kingdom. US officials said a strike from there would be a violation of Iraq’s sovereignty.

The US officials said additional devices, which apparently didn’t reach their targets, were recovered northwest of the facilities and are being jointly analysed by Saudi and American intelligence. The officials, who spoke on condition of anonymity to discuss intelligence matters, did not address whether the drone could have been fired from Yemen, then taken a round-about path, but did not explicitly rule it out.

The attacks and recriminations are increasing already heightened fears of an escalation in the region after a prominent US senator suggested striking Iranian oil refineries in response to the assault, and Iran warned of the potential of more violence.

“Because of the tension and sensitive situation, our region is like a powder keg,” said Iranian Brigadier General Amir Ali Hajizadeh. “When these contacts come too close, when forces come into contact with one another, it is possible a conflict happens because of a misunderstanding.”

Actions on any side could break into the open a twilight war that’s been raging just below the surface of the wider Persian Gulf in recent months. Already, there have been mysterious attacks on oil tankers that America blames on Tehran, at least one suspected Israeli strike on Shiite forces in Iraq, and Iran shooting down a US military surveillance drone.

The attack Saturday on Saudi Arabia’s Abqaiq plant and its Khurais oil field led to the interruption of an estimated 5.7 million barrels of the kingdom’s crude oil production per day, equivalent to more than five per cent of the world’s daily supply. It remains unclear how King Salman and his assertive son, Crown Prince Mohammed bin Salman, will respond to an attack targeting the heart of the Saudi oil industry.