President Trump's national security adviser, John Bolton, asked the Pentagon last fall to develop military options for a strike against Iran following a mortar attack in Baghdad by a Tehran-backed militant group.
In early September, an Iraqi militia with ties to Iran launched mortars towards the United States embassy in Baghdad's diplomatic district.
But they triggered unusual alarm in Washington, where Mr. Trump's national security team led by John Bolton conducted a series of meetings to discuss a forceful American response, including what many saw as the unusual request for options to strike Iran.
The request was met with concern by both the Pentagon and the State Department, according to the Journal, with one former administration official telling the paper that people were "shocked" by the request.
He added: "Sometimes it seems the world has become desensitised to the regime's authoritarianism at home and its campaigns of violence overseas, but the proud Iranian people are not staying silent about their government's many abuses".
Two days later, unidentified fighters fired three rockets that hit close to the U.S. consulate in the southern city of Basra but caused no serious damage.More news: Oil price falls 1% on indecisive US-China trade talks, rising stocks
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The State Department did not comment on the report.
NSC spokesman Garrett Marquis said in a statement on Sunday that "the NSC coordinates policy and provides the president with options to anticipate and respond to a variety of threats" and it will continue to consider "the full range of options" after the attacks in Basra and Baghdad.
While the Pentagon complied with National Security Council's request, it was not clear whether Mr Trump knew of the request or whether plans to strike Iran were seriously considered, the Journal reported.
Relations between Iran and the US have become more confrontational since Trump's election and his May 2018 decision to withdraw from the nuclear deal and reimpose severe economic sanctions on the Islamic Republic.
In September, Bolton, who worked hard on the withdrawal from the treaty, warned Tehran that there would be "hell to pay" if Iran threatened the U.S. or its allies.
Tehran is also believed to be unhappy at comments made by US Secretary of State Mike Pompeo in which he branded Mr Rouhani's regime a "mafia".