Democratic lawmakers in the US Senate and House say the Trump administration’s rationale for attacking Iran remains unconvincing, after a classified briefing led by Secretary of State Marco Rubio and other senior officials.

Senator Richard Blumenthal said the briefing left him “more fearful than ever” that the US could end up deploying ground troops. He added that he was still unclear about the administration’s aims — whether the goal is to destroy Iran’s nuclear capability, target missile systems, pursue regime change, or curb Iran-backed armed groups.

That uncertainty, Democrats warned, increases the risk the US is drawn into a broader and more prolonged conflict.

Senator Chris Murphy said the administration appears to be preparing for further US casualties and warned it is committing the country to an “open-ended engagement with no end in sight”.

In the House, Representative Jason Crow criticised Rubio’s justification for the strikes, arguing it was “very clear” this was a “war of choice” by Trump and that there was no “imminent threat” from Iran that would warrant military action.