(CNN) After an al-Qaeda affiliated group destroyed ancient religious monuments in Timbuktu, Mali, in 2012, the International Criminal Court took on a unique criminal case: prosecuting cultural destruction.

Though it generally focuses on human rights violations, the ICC charged the leader of the jihadist group, Ahmad al-Faqi al-Mahdi, with a war crime for destroying cultural artifacts in Timbuktu.

The case was the first criminal charge of its kind. It "breaks new ground for the protection of humanity's shared cultural heritage and values," UNESCO Secretary-General Irina Bokova said at the time. Al-Mahdi eventually pleaded guilty and was sentenced to nine years in prison

That case has renewed relevance amid the standoff between the United States and Iran days after the United States killed Iranian military commander Qasem Soleimani in a targeted drone strike in Baghdad, Iraq, on Friday.

In a tweet Saturday night , Trump said that if Iran strikes any Americans or American assets, the United States has targeted 52 Iranian sites -- a reference to the number of Americans taken hostage in the 1979 revolution -- "some at a very high level & important to Iran & the Iranian culture," he wrote.

"They attacked us, & we hit back. If they attack again, which I would strongly advise them not to do, we will hit them harder than they have ever been hit before!" Trump wrote.

"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, and we're not allowed to touch their cultural sites? It doesn't work that way," Trump said, according to a pool report.

Secretary of State Mike Pompeo, during an interview with CNN's Jake Tapper on "State of the Union," avoided directly answering whether or not the United States was actually targeting cultural sites and defended Trump's tweeted threat.

"We will be bold in protecting American interests and we'll do so in a way that is consistent with the rule of law. We've always done that, Jake, and President Trump's tweet doesn't deviate from that one iota," he said.

"So cultural centers are theoretically fair targets, in your view?" Tapper asked.

"We're going to do the things that are right and the things that are consistent with American law," Pompeo said.

Destroying cultural sites as war crime

Protesters shout slogans against the United States and Israel as they hold posters with the image of Qasem Soleimani, who was killed in a US airstrike in Iraq, and Iranian President Hassan Rouhani during a demonstration in the Kashmiri town of Magam on January 3.

However, an attack on a cultural site would violate several international treaties and would likely be considered a war crime.

In 2017, for example, a United Nations Security Council resolution "condemns the unlawful destruction of cultural heritage, including the destruction of religious sites and artifacts." That resolution came as a response to the Islamic State's destruction of a number of major historic and cultural sites in Syria and Iraq in 2014 and 2015.

The UN was clear then that actions targeting cultural locations constituted a war crime.

"The deliberate destruction of our common cultural heritage constitutes a war crime and represents an attack on humanity as a whole," said the spokesman for then-UN Secretary-General Ban Ki-moon in 2015.

Nicholas Burns, former undersecretary of state for political affairs and ambassador to NATO, noted the Trump administration supported the 2017 UN resolution condemning destruction of cultural sites.

"His threat is immoral and Un-American," Burns wrote on Twitter.

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Hossein Dehghan, the main military adviser to Iran's Supreme Leader Ayatollah Khamenei, said Trump's tweets are "ridiculous and absurd." He told CNN that Iran's response "will be military and against military sites."

If the United States does carry out Trump's threat to strike any of Iran's cultural sites, then "for sure no American military staff, no American political center, no American military base, no American vessel will be safe," Dehghan said. "If he says 52, we say 300, and they are accessible to us."

In a tweet, Iran Foreign Minister Javad Zarif said an attack on a cultural site is a war crime.

"Having committed grave breaches of (international) law in Friday's cowardly assassinations, (Trump) threatens to commit again new breaches of JUS COGENS," he said, referring to the phrase for international law norms. "Targeting cultural sites is a WAR CRIME"

"Those masquerading as diplomats and those who shamelessly sat to identify Iranian cultural & civilian targets should not even bother to open a law dictionary," he continued . "Jus cogens refers to peremptory norms of international law, i.e. international red lines. That is, a big(ly) 'no no.'"

US officials say widespread opposition to targeting cultural sites

Two senior US officials on Sunday described to CNN's Jim Sciutto widespread opposition within the Trump administration to targeting cultural sites in Iran.

"Nothing rallies people like the deliberate destruction of beloved cultural sites. Whether ISIS's destruction of religious monuments or the burning of the Leuven Library in WWI, history shows targeting locations giving civilization meaning is not only immoral but self-defeating," one of the officials told CNN.

Another official who formerly worked in both the Trump and Obama administrations told CNN: "As a matter of principle, we as a nation and as a military do not attack the culture sites of any adversary."

Additionally, several sources told CNN there are no indications -- aside, perhaps, from Trump's tweet -- that the United States would actually strike cultural sites in Iran.

Colin Kahl, former deputy assistant to President Barack Obama and national security adviser to Vice President Joe Biden, expressed skepticism that there are actually cultural sites on the list of possible retaliatory sites.

"For what it's worth, I find it hard to believe the Pentagon would provide Trump targeting options that include Iranian cultural sites," he tweeted . "Trump may not care about the laws of war, but (Department of Defense) planners and lawyers do...and targeting cultural sites is (a) war crime."