Defense Secretary Pete Hegseth and Joint Chiefs Chairman Gen. Dan Caine speak during a news conference at the Pentagon in Washington, Sunday, after the U.S. military struck three sites in Iran, directly joining Israel's effort to destroy the country's nuclear program. (AP-Yonhap)
Defense Secretary Pete Hegseth and Joint Chiefs Chairman Gen. Dan Caine speak during a news conference at the Pentagon in Washington, Sunday, after the U.S. military struck three sites in Iran, directly joining Israel's effort to destroy the country's nuclear program. (AP-Yonhap)

The US military used 14 GBU-57 bunker-busting bombs in its overnight attacks on key Iranian nuclear sites, the Pentagon said on Sunday.

The powerful bombs were dropped on two nuclear facilities, Chairman of the Joint Chiefs of Staff Dan Caine said during a press conference, hours after the US intervened in the conflict against Iran on behalf of Israel.

It comes after US President Donald Trump said US aircraft attacked three nuclear sites in Iran overnight, including Natanz, Isfahan and the Fordow uranium enrichment facility - widely believed to be one of Israel's most critical war targets.

The move marks a serious escalation in the war between Israel and Iran, amid already heightened fears of a wider regional conflict.

Iran has said the US intervention will lead to "everlasting consequences," amid concern that Iran might retaliate by targeting US bases in the region.

Israel launched widespread airstrikes across Iran on June 13, saying it is aimed at preventing Iran from developing a nuclear weapon - a charge that Tehran has consistently denied. (DPA)