Defense Secretary Mark Esper said the United States would not target Iranian cultural sites should tensions with Tehran escalate into an armed conflict, contradicting President Donald Trump’s vows to hit the country “very fast and very hard” if Iran retaliates for the assassination of one of its military leaders.

“We will follow the laws of armed conflict,” Esper said during a news conference at the Pentagon on Monday, according to The New York Times. In response to a question from a reporter, Esper agreed that such rules barred the targeting of cultural sites.

His comments come amid an international outcry over the plan, first touted (and then repeated) in a series of tweets by Trump this weekend. The president said on Saturday that the U.S. had selected 52 sites to target in Iran should the country attack any American assets, including some sites that “at a very high level & important to Iran & the Iranian culture.”

Tensions with Tehran have risen since Trump ordered the assassination of Iranian Maj. Gen. Qassem Soleimani, one of the most powerful military figures in the Middle East, in a drone strike in Iraq.

The killing sparked fury within Iran, which ended its remaining commitments to limit nuclear fuel production that had been negotiated as part of the Iran nuclear deal. The country has also pledged to respond to the assassination in a “crushing and powerful manner.”

Trump’s calls that cultural sites be targeted also prompted international rebukes as many noted it would constitute a war crime under international law. But despite that criticism, Trump reiterated his pledges in remarks to reporters on Sunday.

“They’re allowed to kill our people,” Trump told journalists traveling on Air Force One. “They’re allowed to torture and maim our people. They’re allowed to use roadside bombs and blow up our people. And we’re not allowed to touch their cultural site? It doesn’t work that way.”

Esper defended the Baghdad drone strike on Monday, saying the U.S. was compelled to respond after the Pentagon learned Soleimani was planning attacks on American forces.

“How do you expect us not to respond when they’ve been killing our people for 20 years?” Esper said. “Soleimani alone has the blood of hundreds of Americans; he’s wounded thousands of American coalition partners. He is a terrorist, a leader of a terrorist organization who’s been killing and attacking Americans for 20-some years, and the blood is on his hands.”

White House aides went on the defensive Monday, saying Trump didn’t, in fact, say he would target cultural sites despite his repeated remarks.

“He didn’t say he’s targeting cultural sites,” White House counselor Kellyanne Conway told reporters, according to The Hill. “He said that he was openly asking the question why in the world they’re allowed to maim people, put out roadside bombs, kill our people, torture our people ... he said that they identified 52 sites.”