Reporting from Washington DC, Al Jazeera’s Kimberly Halkett says Donald Trump’s latest remarks on the conflict with Iran are significant because they mark the first time reporters have been able to question him directly after several days of shifting explanations for why the US joined Israel in launching attacks.

A central question put to Trump was whether Israel had effectively forced Washington’s hand. The issue has gained traction after Secretary of State Marco Rubio said on Monday that the US took “pre-emptive” military action based on an expectation that Israel was going to strike Iran — and to avoid Iranian retaliation.

Halkett said Trump’s account in the Oval Office differed. He argued the US believed Iran was “one month” from a nuclear weapon and claimed Iran was preparing to attack Israel — which, he said, was why the US struck first.

Halkett added that the evolving rationale is likely to be heavily scrutinised in the US, where the president’s authority to launch military action without Congress is contested and typically tied to an imminent threat. Trump, she noted, has not presented evidence publicly of a direct threat to the United States, instead pointing to a perceived risk to Israel.