Donald Trump insisted on Tuesday that the war in Iran enjoys widespread support amongst Americans, with his view bolstered, according to him, by the revelation that a major US city was threatened by Iran's nuclear weapons development programme.

Since American and Israeli bombs struck Tehran in February, the president's approval ratings have nosedived while petrol prices have rocketed across the nation.

Speaking to reporters on Tuesday at the construction site for the White House ballroom, Trump acknowledged some negative sentiment towards the conflict, which is approaching its third month.

"Everyone tells me it's unpopular, but I think it's very popular," Trump said. "When they hear that it has to do with nuclear weapons that could take out Los Angeles, take out major cities very quick - I'll tell you what when we explain it to people - I don't really have enough time to explain it to people. I'm too busy getting it done."

However, a fresh New York Times and Sienna poll published Monday joins a mounting collection of surveys indicating the Iran war is deeply unpopular with the public.

Pollsters asked whether Trump's decision to go to war with Iran was the right or wrong call. An overwhelming majority - 64% of respondents - said it was the wrong decision. Just 30% backed the president.

The conflict and surging petrol prices, as other polls have demonstrated, are dragging down Trump's approval ratings and potentially endangering down ballot Republicans ahead of the midterm elections.

"As both parties mobilize for expensive and bitter midterm contests, the survey suggests that Republican candidates are entering their general-election races with stark political liabilities," pollsters at the New York Times said.

These policies are additionally impacting his overall approval rating, with the Times poll registering a fresh record low for his second term at merely 37%. The survey was carried out between May 11-15 amongst 1,507 registered voters.

However, despite mounting disapproval of Trump's foreign policy, he reaffirmed his stance on the Iran conflict when addressing reporters' questions on Tuesday.

"I think frankly it's very popular. But whether it's popular or unpopular, I have to do it," Trump said, "because I'm not going to let the world be blown up on my watch. Not gonna happen."

The President responded to questions in front of another priority undermining his popularity -- the White House ballroom, which has proved contentious since Trump unveiled the project in October.

A Washington Post-ABC News poll released earlier this month revealed Americans remain opposed to the ballroom proposal as much as they were last autumn.

The survey showed they reject the East Wing's demolition and ballroom project 56% to 28%, identical percentages to when the poll was conducted in October.