The Pentagon is distancing itself from President Donald Trump’s assertions that he would bomb Iranian cultural sites. Such attacks would violate international prohibitions.

Defense Secretary Mark Esper says the U.S. will “follow the laws of armed conflict.” When asked if that ruled out targeting cultural sites, Esper said, “That’s the laws of armed conflict.”

The split between the president and his Pentagon chief comes amid heightened tensions with Tehran following a U.S. strike that killed the head of Iran’s elite Quds force, Gen. Qassem Soleimani.

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Trump on Saturday tweeted that if Iran responded by attacking Americans or American assets, the U.S. had already picked 52 targets "some at a very high level & important to Iran & the Iranian culture." The 52 targets represent the 52 Americans taken hostage in Iran in 1979 and held for 444 days.

Trump doubled down on the threat Sunday.

“They’re allowed to kill our people. They’re allowed to torture and maim our people. They’re allowed to use roadside bombs and blow up our people,” Trump reportedly said. "And we’re not allowed to touch their cultural sites? It doesn’t work that way."

But international law that both the U.S and Iran signed says it does.

The 1954 Hague Convention for the Protection of Cultural Property in the Event of Armed Conflict was adopted following the massive destruction of cultural heritage during World War II, according to the United Nations. The convention calls on nations "to take all possible steps to protect cultural property."

It also states countries should not use cultural sites as locations to shield legitimate military targets.

The convention applies to the use of conventional weapons.