US President Donald Trump said on Wednesday there were many options short of war with Iran after US ally Saudi Arabia displayed remnants of drones and missiles it said were used in a crippling attack on its oil sites that was “unquestionably sponsored” by Tehran.

“There are many options. There’s the ultimate option and there are options that are a lot less than that. And we’ll see,” Trump told reporters in Los Angeles. “I’m saying the ultimate option meaning go in — war.”

Trump said on Twitter that he had ordered the US Treasury to “substantially increase sanctions” on Iran, which denies carrying out the attacks, and told reporters the unspecified, punitive economic measures would be unveiled within 48 hours.

Trump’s tweet followed repeated US assertions that the Islamic Republic was behind Saturday’s attacks and came hours after Saudi Arabia said the strike was a “test of global will”.

The president struck a cautious note as his Secretary of State Mike Pompeo on Thursday, during a visit to Saudi Arabia, described the attacks as “an act of war” on the kingdom, the world’s largest oil exporter, and said America backs Saudi Arabia’s “right to defend itself”.

Iran, which has denied involvement in the attack, warned the US it will retaliate immediately if it is targeted.

The attacks have reignited fears over a wider conflagration in the region, as tensions remain high over Iran’s collapsing nuclear deal with world powers.

Pompeo’s comments on Twitter came after meeting with Saudi Crown Prince Mohammed bin Salman, the kingdom’s defense minister. The Saudis on Wednesday displayed missile and drone wreckage and cited other evidence they alleged shows the raid was “unquestionably sponsored by Iran”.

Pompeo called the attacks “unprecedented”. “The Iranian regime’s threatening behavior will not be tolerated.”

Pompeo was to next visit the United Arab Emirates to meet with Abu Dhabi’s powerful crown prince, Sheikh Mohammed bin Zayed Al Nahyan. The UAE is a close ally of Saudi Arabia and joined the kingdom in its war in Yemen against the Houthis.

The UAE announced on Thursday it had joined a US-led coalition to protect waterways across the Mideast after an attack on Saudi oil installations.

The state-run WAM news agency quoted Salem al-Zaabi of the Emirati Foreign Ministry as saying the UAE joined the coalition to “ensure global energy security and the continued flow of energy supplies to the global economy”.

Saudi Arabia joined the coalition on Wednesday. Australia, Bahrain and the United Kingdom also are taking part.

The US formed the coalition after attacks on oil tankers that American officials blame on Iran, as well as Iran’s seizure of tankers in the region. Iran denies being behind the tanker explosions, though the attacks came after Tehran threatened to stop oil exports from the Persian Gulf.