A Reuters/Ipsos poll found that only one in three Americans support the US war in Iran, the lowest level recorded since the conflict began five months ago. The result highlights public concern over the war’s purpose and costs, creating a political challenge for President Donald Trump and congressional Republicans ahead of November’s midterm elections.

Sixty-nine per cent said Trump had not clearly explained the US objectives, which have included preventing an Iranian nuclear weapon, limiting ballistic missiles and supporting political change in Iran. The online survey of 1,246 adults, conducted from Friday to Sunday, had a three-point margin of error; 18 US service members have died, while average petrol prices have risen from about $3 to just over $4 per gallon.