In his first major speech since joining the White House, National Security Advisor John Bolton on Monday threatened sanctions against judges in the International Criminal Court if they continue attempting to probe alleged American war crimes in Afghanistan.

Over the past decade, the prosecutor of the International Criminal Court has conducted a preliminary examination of allegations of war crimes and crimes against humanity in Afghanistan. But in November 2017, the the prosecutor moved a step further and requested authorization to investigate the alleged crimes carried out not only by members of the Taliban, but also by U.S. intelligence and service members during the war.

In a speech from the Mayflower Hotel in Washington, D.C., Bolton, on the eve of Sept. 11, denounced the court and said the U.S. would not cooperate with its inquiries.

“The United States will use any means necessary to protect our citizens and those of our allies from unjust prosecution by this illegitimate court,” Bolton said. “We will let the ICC die on its own. For all its intents and purposes, [it] is already dead to us.”

During a press conference, Bolton said the ICC’s investigations threatened the sovereignty of the U.S. After a question from the audience, Bolton pushed back on the assertion that the U.S. had in fact threatened the autonomy of others. “I don’t think we're threatening anyone else's sovereignty,” he said.

“The Trump administration has a very different view of the ICC than the Obama administration,” Bolton said. “So we wanted to be out there on the record about that.”

Human rights advocates told The Daily Beast that they viewed Bolton’s remarks as an attempt by the U.S. to intimidate the court into dropping its inquiries into the crimes allegedly carried out by American servicemen.

James Goldston, the executive director of Open Society Justice Initiative, which advances the rule of law and rights protection worldwide, said the U.S. has at times engaged in conversations and meetings about the court’s activities. It also supports the court’s investigations into various war criminals such as Joseph Kony, the leader of the Lord’s Resistance Army in Uganda.

But, he said, the U.S. has also demanded that activities carried out by American individuals should not fall under the court’s purview. The U.S. is a signatory to the Rome Statute, the treaty that established the ICC, but did it did not ratify the statute, which means it is not a member of the court.

“The relationship between the U.S. and the ICC has been fraught but variable since the late 1990s,” Goldston said. “But this is a forceful response and represents an unfortunate … turn of events. The response is premature given the reality of what the court is likely to focus on in Afghanistan.”

Goldston said that the ICC, while it notes its interest into alleged crimes committed by U.S. servicemen, is likely to first target the most widespread and egregious crimes carried out during the war—those committed by the Taliban and members of the Afghan Security Forces.

“Even once an investigation is launched it has historically taken years to carry out,” Goldston said.

If the ICC probe into American activities in Afghanistan proceeds, the Trump administration will look at banning judges from entering the U.S. and put sanctions on any funds they hold in the country.

Bolton also called out the court for its preliminary examination into alleged crimes carried out by Israel in Palestinian territories. His remarks followed an announcement by the State Department and the White House that the administration would close the Palestinian Liberation Organization’s diplomatic offices in Washington, D.C. after its call for an ICC inquiry into Israel.

“The United States will always stand with our friend and ally, Israel,” Bolton said. “The Trump administration will not keep the office open when the Palestinians refuse to take steps to start direct and meaningful negotiations with Israel.”

On Monday morning, low level staffers working in the consulate section of the PLO office sat inside, unsure if they, too would need to leave their posts. Staffers said they did not find out about the office’s closing until late Sunday night after the Wall Street Journal broke the story.

The announcement about the closure of the PLO office comes after months of the Trump administration.

In May, Trump opened a U.S. embassy in Israel in Jerusalem, causing uproar by Palestinians who claim its the eastern parts of the city as their own. Following the opening of the embassy, Palestinian president, Mahmoud Abbas, recalled his envoy to the U.S.

Days later, the Palestinian foreign minister asked the ICC prosecutor to open an investigation into alleged Israeli war crimes and crimes against humanity. Israel is also not a member of the ICC and has also said the court lacks jurisdiction over its citizens.

“This afternoon, we also make a new pledge to the American people,” Bolton said. “If the court comes after us, Israel or other U.s. allies, we will not sit quietly.”

“John Bolton’s threats show callous disregard for victims of atrocity crimes. The Trump administration claims to support accountability for grave abuses, but undermining the ICC would only squander opportunities for justice,” said Liz Evenson, associate international justice director at Human Rights Watch.