Iran has sharply stepped up efforts to target American officials, with some lethal plots now at an advanced stage, the top US intelligence official has warned Secretary of State Marco Rubio, as Washington pulls diplomats out of Saudi Arabia and trims staff at several other embassies in the region.

In a one-page unclassified memo dated October 23, Director of National Intelligence Jay Clayton told Rubio that Iran had “substantially increased efforts to target U.S. personnel”, Axios reported, citing the document. The memo, copied to CIA Director John Ratcliffe, said lethal plots had “reached advanced stages in both the Middle East and certain other countries”, according to Axios’s Barak Ravid, who first reported it.