"I have just instructed the Secretary of the Treasury to substantially increase Sanctions on the country of Iran!" he tweeted while traveling in California.
Trump made the announcement as Secretary of State Mike Pompeo was headed to Saudi Arabia to discuss how to respond to the attack, which Pompeo has blamed on Iran but Trump has not done so publicly.
In August, the U.S. placed sanctions on Iranian Foreign Minister Javad Zarif, which Iran called "childish."
In June, Trump announced what he called "hard hitting" sanctions on Iran, including on Supreme Leader Ayatollah Ali Khamenei.