The attack on a major Saudi oil facility originated geographically from Iranian territory, with a series of low-altitude cruise missiles fired from at least one location in the western region of the country, according to two U.S. officials familiar with the latest intelligence.
The intelligence assessment draws a more clear link between the attack and Iran, and it could worsen tensions between Washington and Tehran.
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U.S. officials are considering possible multilateral sanctions with allies against Iran as part of the response to the attacks on Aramco's main crude processing facility, which knocked out 5.7 million barrels of daily oil production for Saudi Arabia, or more than 5 percent of the world's daily crude production, analysts have said.
The Department of Defense has advocated for restraint. But it has provided a briefing on military options to President Donald Trump, who over the weekend tweeted that the U.S. is "locked and loaded" and ready to respond, once it officially determined who was behind the attack.
Three U.S. officials previously told NBC News there was extremely compelling evidence showing the origination point of the strikes, and one official with direct knowledge described that evidence as imagery.
A Saudi military spokesman says initial investigations show Iranian weapons were used in the attack.
Iran's Supreme Leader Ayatollah Ali Khamenei said Tuesday no talks would take place between Iran and the U.S. "on any level," remarks that apparently meant to end all speculation about a U.S.-Iran meeting at the United Nations later this month.
"All officials in Iran have one united voice to not negotiate with the U.S. on any level," he told Iranian state television.