Saudi Arabia's defence ministry has shown off what it says is wreckage of drones and cruise missiles that proves Iranian involvement in weekend attacks on two oil facilities.
It said 18 drones and seven cruise missiles were fired from a direction that ruled out Yemen as a source.
Yemen's Iran-aligned Houthi rebels have said they are behind the attacks.
Iran has denied any involvement and warned it would retaliate against any attack that targeted it.
The US has stood by its accusation that Iran was behind the attacks. Secretary of State Mike Pompeo said after arriving in Saudi Arabia on Wednesday that it was an "act of war".
President Donald Trump said the US had "many options" in response.
"There is the ultimate option, and there are options a lot less than that," he said. "And we'll see. We are in a very powerful position."
The evidence was presented at a defence ministry press briefing, where debris from the drone (UAV) and missile attacks was laid out.
Defence ministry spokesman Col Turki al-Malki said the evidence showed the attacks were launched from the north and were “unquestionably sponsored by Iran”.
However, Col Malki said the Saudis were still "working to know exactly the launch point".
Abqaiq - run by the Saudi state oil company, Aramco - and the Khurais oilfield were hit in the early hours of Saturday.
The Houthis have repeatedly launched rockets, missiles and drones at populated areas in Saudi Arabia. They are in conflict with a Saudi-led coalition which backs a president who the rebels had forced to flee when the Yemeni conflict escalated in March 2015.
Iran is the regional rival of Saudi Arabia and an opponent of the US, which pulled out of a treaty aimed at limiting Tehran's nuclear programme after Mr Trump took power.
US-Iran tensions have risen markedly this year.
The US said Iran was behind attacks on two oil tankers in the Gulf in June and July, as well as on another four in May. Tehran rejected the accusations in both cases.