US, Saudi agree with 'high probability' Aramco attack was launched from Iran
The official, who declined to be identified, said the US was gathering evidence about the attack to present to the international community, notably European allies, at the UN General Assembly next week.
Investigators from both Saudi Arabia and the US believe the missiles travelled over southern Iraq and through Kuwaiti airspace before hitting the state-owned oil processing plants in Saudi Arabia's east, a similar report from CNN said on Tuesday.
Kuwait's interior ministry said on Monday it was investigating the sighting of a drone over its territory just before the strikes on Saudi Arabia's oil facilities.
The strikes on Abqaiq - the world's largest oil processing facility - and the Khurais oil field in eastern Saudi Arabia have roiled global energy markets and caused prices to spike on Monday.
Yemen's Iran-aligned Houthi rebels claimed they carried out the attacks with ten drones, but American media have reported that US officials had satellite images showing the attacks - possibly with drones and cruise missiles - had come from the north or northwest, rather than Yemen.
The Saudi-led coalition on Monday said its preliminary probe had found Houthi rebels were not responsible, while squarely pointing the finger at Iran for providing the weapons used in the attacks.
It said it was still investigating where the strikes had originated.
Iraq, home to several Iran-backed paramilitary factions, has been placed in an awkward situation amid rising tensions between its two main allies, Iran and the US.
Baghdad has denied the attacks were launched from its country, with Prime Minister Adel Abdel Mahdi reiterating Iraq's aim to stay neutral in a call with US Secretary of State Mike Pompeo on Monday.