According to the report, Washington has already deployed sufficient military assets in the region to carry out the attacks. However, Trump has yet to decide whether to authorise a fresh offensive against Tehran.
“It will be a big effort,” one US official told CNN, indicating that the military preparations could extend beyond limited strikes on Iranian radar systems, missile launchers and other military targets.
The US Central Command and the Pentagon have reportedly been developing a broader list of potential targets, including Iran's energy infrastructure, military installations and nuclear facilities.
Trump may delay Iran strikes until after US midterm elections
Current and former US officials familiar with the military planning believe a decision on fresh strikes could come before the end of the year, with the period after the US midterm elections emerging as a possible window for action.
However, officials cautioned that Trump has previously appeared inclined towards certain military operations before backing away at the last moment.
A senior Pentagon official told CNN that the department's role was to prepare options for the president.
“The Department is a planning organisation, and its job is to develop and execute military options ordered by the President,” the official said.
Iran, Houthis could retaliate against US targets
The military preparations come amid growing concerns within the US intelligence community that Iran and Yemen's Houthi rebels could retaliate if Washington and Israel launch another round of attacks.
Sources familiar with intelligence assessments told CNN that Tehran and the Houthis are taking the prospect of renewed US strikes seriously.
If Iran is attacked, both could respond against American personnel and facilities across the region. The retaliation could potentially extend beyond the Middle East, according to the report.
An October 23 memo from Director of National Intelligence Jay Clayton to Secretary of State Marco Rubio reportedly warned that Iran had significantly intensified efforts to target US personnel.
The memo said plotting efforts had reached advanced stages in the Middle East and certain other countries, CNN reported.
US intelligence officials reportedly assess that Iran and the Houthis are unlikely to launch pre-emptive attacks against American personnel or Israel at present. However, the risk of retaliation could rise sharply if US or Israeli forces strike Iran first.
Israel sought joint attack before elections, report says
Israel had been preparing for the possibility of renewed strikes against Iran and had sought Washington's support for a joint operation, according to sources cited by CNN.
“Netanyahu really wanted and tried to convince Trump for a joint attack in Iran before the elections, and Trump did not give a green light,” an Israeli security source told the network.
The Israeli Prime Minister's Office dismissed the allegation as “fake news”.
According to the source, one factor in the decision to hold back was a warning from Israeli military chief Eyal Zamir to US General Dan Caine, chairman of the Joint Chiefs of Staff, that an attack could affect Israel's elections and potentially force their postponement.
Senior US officials, including Trump, reportedly urged Israel to refrain from further strikes for the time being, while leaving open the possibility of coordinated military action later.
Israel has since postponed its immediate plans but continues to prepare for a potential joint operation with Washington, the sources said.
Israel's missile defence needs could shape timing
Israel's decision to delay further attacks was also linked to concerns over its ability to defend against Iranian and Houthi retaliation, according to a source briefed on the matter.
The country's defensive missile stockpiles have been strained during the conflict, making American military support particularly important in the event of renewed hostilities.
Meanwhile, Israeli Prime Minister Benjamin Netanyahu said at an Israeli military graduation ceremony this week that he had instructed the military, the Mossad and other security agencies to work towards toppling the Iranian regime.
With US military planning reportedly advancing and Israel continuing to prepare for possible action, the timing of any fresh offensive will depend on Trump's decision.
Sources cited by CNN indicated that a joint operation could potentially take place after the US midterm elections, although no final decision has been announced.