The ‘mind-boggling’ request came after two incidents in Iraq last September when militia mortar and rockets exploded near US diplomatic facilities

The White House asked the Pentagon to draw up options for military strikes against Iran in the wake of two incidents in Iraq last September when mortar shells and rockets fired by militias exploded near US diplomatic facilities, it was reported on Sunday.

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Contingency planning for potential conflicts is routine, but according to the Wall Street Journal, the seriousness of the request from the National Security Council unnerved defense and state officials.

“It definitely rattled people,” a former senior US administration official was quoted as saying. “People were shocked. It was mind-boggling how cavalier they were about hitting Iran.”

A direct US attack on Iran would be risk triggering a conflict between the two nations that would be hard to stop. There are already hardliners in both camps calling for military confrontation.

The secretary of state, Mike Pompeo, declined to comment on the report on Sunday, when questioned by reporters on his nine-nation tour of the Middle East, which is aimed in large part at maintaining Arab solidarity against Iran. On Sunday he flew from Qatar to Saudi Arabia, where he is due to meet Crown Prince Mohammed bin Salman.

In Qatar, Pompeo provided details of a planned anti-Iran ministerial conference to be held, at US prompting, in Warsaw in February.

“There’ll be a broad coalition of countries present,” he said, “and we’ll work on many issues, including how it is we can get the Islamic Republic of Iran to behave more like a normal nation.”

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Since John Bolton, the former US ambassador to the United Nations, became national security adviser in April last year, he has joined with Pompeo in pushing for a much more aggressive posture towards Tehran. Bolton, who wrote a New York Times commentary in 2015 calling for Iran to be bombed, warned that Tehran would have “hell to pay” if it threatened the US or its allies.

That warning came after a Shia militia fired three mortar shells on 6 September into the diplomatic district of Baghdad, where the US has its embassy. A few days later, missiles fired by unknown militants fell near the US consulate in the southern Iraqi city of Basra.

Although there were no casualties or significant damage in either incident, they raised alarm in Washington that US diplomats could be vulnerable.

“We have told the Islamic Republic of Iran that using a proxy force to attack an American interest will not prevent us from responding against the prime actor,” Pompeo told CNN at the time, making clear a military response was possible.

Later on Sunday, Axios reported that James Mattis, the then defense secretary, had “deep concerns” about the White House request at the time, believing that it risked creating a direct conflict with Iran.

Last year, Donald Trump pulled the US out of a multilateral 2015 nuclear deal with Iran. He has ordered a campaign of intense sanctions against the Islamic Republic. But he also reassured European leaders that he did not want to be drawn into a new Middle Eastern conflict, and that he would rein in Bolton.

The president’s order for US troops to withdraw from Syria, where they were near Iranian troops and Iranian-backed militias, marked a defeat for Iran hawks in his administration. But with hardliners in positions of influence on both sides, the potential for an unplanned clash remains high, particularly in the crowded sea lanes of the Gulf or in Iraq.

The tough talk from Bolton and Pompeo has added to concerns that Baghdad could again become a proxy battleground between the US and Iranian interests, much as it was during the height of the sectarian chaos, when a full-blown proxy war played out across the country.

Throughout much of the US military presence in Iraq, the giant US embassy in the Iraqi capital’s fortified Green Zone was a target for Shia militias, which regularly rained in rockets and mortars from as far as seven miles away.

Two of the main protagonists from 2007 to 2011, Asa’ib ahl al-Haq and Kataib Hezbollah, both proxies of Iran’s Revolutionary Guards Corps, have gained strength in Baghdad in the past four years, and exert considerable influence across political and security spheres.

Conflict could also be triggered if Iran decides to abandon the 2015 nuclear deal. The US abrogation of the agreement means Tehran is receiving few of the economic benefits it was promised.

On Sunday, the head of the country’s nuclear programme, Ali Akbar Salehi, said technicians had begun “preliminary activities for designing” a new way of producing 20%-enriched uranium. If production was resumed, it would violate the 2015 agreement, which still exists with other world powers despite the US pulling out, and would escalate tensions with Israel, the Gulf states and the US.

The National Iranian American Council (NIAC), a pro-diplomacy advocacy group, issued a statement on the Wall Street Journal report, saying: “This administration takes an expansive view of war authorities and is leaning into confrontation with Iran at a time when there are numerous tripwires for conflict across the region.”