Media reports say US airstrikes on Iranian nuclear facilities did not destroy the core components of the country's nuclear program, and likely only set it back by months.

CNN and other US media outlets on Tuesday attributed the findings to an early assessment produced by the US Defense Intelligence Agency.

The US military on Sunday used ground-penetrating munitions, known as bunker buster bombs, and Tomahawk missiles to strike three Iranian nuclear facilities.

CNN quotes sources familiar with the assessment as saying that Iran's stockpile of enriched uranium was not destroyed, and that its centrifuges are largely "intact."

The assessment appears to be at odds with US President Donald Trump's assertion that the strikes "completely and totally obliterated" Iran's nuclear enrichment facilities.

White House Press Secretary Karoline Leavitt posted on social media that "this alleged statement is flat-out wrong."

She added, "Everyone knows what happens when you drop fourteen 30,000 pound bombs perfectly on their targets: total obliteration."