Iran has "substantially increased" its efforts to target Americans in the Middle East and beyond, US national intelligence chief Jay Clayton warned on Friday.
The warning comes after Washington ordered non-essential US embassy staff and their families to leave Saudi Arabia this week, following increasing attacks from Yemen's Houthis.
The kingdom has come under near-daily attacks this month from the Iran-backed group, including a strike on Riyadh's international airport that was the kingdom's deadliest in years.
"We have received intelligence that Iran has substantially increased efforts to target US personnel," Clayton said in a memo sent to Secretary of State Marco Rubio, according to a US official.
"The lethal plotting efforts by the Iranians against US citizens have reached advanced stages in both the Middle East and certain other countries," said the memo, which was first reported by Axios.
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The US previously ordered non-essential staff to leave the Gulf ahead of the start of its war against Iran and again in July before US President Donald Trump called off a new wave of strikes.
The US official said: "When it comes to our staffing at embassies, we constantly evaluate new information about the security environment."
"The threat of Houthi attacks and of Iranian terror plots targeting US officials are informing our decisions," the official added.
Trump suggested on Friday that the US might launch renewed military operations against Iran.
"We may do another little Epic Fury" Trump said, referring to the US name for its attacks on Iran. He did not give any indication on timing.
The conflict began in late February with US-Israeli attacks on Iran, killing the country's supreme leader, along with senior military commanders.
