Washington DC - Republican Senator John Kennedy broke ranks and let it slip that President Donald Trump's administration is likely to blame for a devastating missile strike on a girls' school in Iran.

Kennedy on Monday told a reporter from NBC News that he was "just so sorry" for the killing of at least 175 people, mostly children, at an elementary school in Minab, Iran, on the first day of Trump's devastating war.

"It was terrible. We made a mistake," Kennedy said. "Other countries do that sort of thing intentionally, like Russia. We would never do that intentionally. I think the department is investigating it now, and I'm sorry."

Recent reports indicate the strike was likely carried out by a Tomahawk missile, which is exclusively manufactured in the US and possessed only by a few close allies such as the UK and Australia.

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Despite this, Trump has repeatedly and baselessly insisted that Iran had bombed the school, contrary to all other claims.

Human Rights Watch and numerous other human rights organizations are calling for a war crime probe into the attack.

Kennedy has generally stood firmly behind the Trump administration's decision to wage a devastating war on Iran, writing on Tuesday that Iran's "leaders are nuts... The president did the right thing."

Speaking on CNN's The Arena with Kasie Hunt, however, Kennedy again broke Trump's narrative and said he's "not going to hide behind" the ongoing investigation, as other officials have done.

"It was a terrible, terrible mistake. The investigation may prove me wrong – I hope so. The kids are still dead, but I think it was a horrible, horrible mistake," Kennedy said.

"I wish it hadn't happened. I'm sorry it happened. I assure you it wasn't intentional."