The United States is reducing embassy staffing in several Middle Eastern countries after American intelligence agencies warned that Iran has intensified efforts to assassinate US officials and diplomats abroad, Axios reported.

According to the Axios report, an October 23 intelligence memorandum addressed to US Secretary of State Marco Rubio states that Iranian assassination efforts have "substantially increased," with some plots reaching "advanced stages."

The warnings concern potential attacks in the Middle East and elsewhere, although the memorandum does not identify specific targets, describe the planned operations or name the countries outside the region where attacks could occur.

Earlier this week, the US State Department ordered family members and nonessential personnel to leave the US Embassy in Riyadh and the American consulates in Jeddah and Dhahran.

On Friday, additional staffing reductions were ordered at US diplomatic missions in the United Arab Emirates, Lebanon, Qatar and Jordan, according to an American official cited by Axios.

The embassies in the UAE, Lebanon, Qatar and Jordan remain open under restricted operations, and personnel have not been ordered to leave, unlike the designated employees and family members at US diplomatic missions in Saudi Arabia.

The intelligence memorandum, obtained by Axios, was sent to Rubio by Director of National Intelligence Jay Clayton. It warns that information concerning the suspected Iranian assassination plots needs to be shared with a wider group of US government personnel than those currently authorized to receive it.

Clayton offered to lower the classification level of as much of the relevant intelligence as possible, allowing the State Department to distribute the warnings more broadly to personnel potentially facing danger.

The memorandum indicates that senior State Department officials have already received the underlying intelligence.

The developments come amid concerns about another military confrontation involving Iran, Israel and the United States, potentially following the November 3 American midterm elections.

At a rally in Florida on Friday, US President Donald Trump raised the possibility of renewed US military action against Iran if Tehran does not reach an agreement with Washington.

"We may do another little Operation Epic Fury, or [the Iranians] will agree [to a deal]," Trump said. "If they're smart, they will just say, 'Let's get down to business,' but I doubt they will do that because perhaps they're not smart."