Iran has ramped up efforts to target U.S. personnel, and lethal plots by Tehran against American citizens have reached “advanced stages,” a senior intelligence official in the Trump administration warned in a memo seen by reporters.

The alert from Director of National Intelligence Jay Clayton came after Washington scaled back staffing at its mission in Saudi Arabia last week in response to intensified attacks by Iran-allied Houthi forces.

Those attacks on one front of the nearly 8-month-old regional conflict triggered by the Iran war have coincided with a rise in attacks on commercial shipping in the Strait of Hormuz.

Earlier this month, sources said Iran was preparing a more forceful response if the United States resumes large-scale military attacks on its territory.

“Specifically, through various channels, we have received intelligence that Iran has substantially increased efforts to target U.S. personnel,” Clayton wrote to U.S.…