The Trump administration on Monday threatened to impose sanctions on International Criminal Court (ICC) personnel if it continues with an investigation into alleged U.S. war crimes in Afghanistan, a move that could raise questions about the future of the court.

National security adviser John Bolton, a longtime ICC critic, made the announcement in his first major speech since joining the Trump administration.

"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 told members of the conservative Federalist Society gathered at a Washington, D.C., hotel.

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The top security official argued the court poses a threat to U.S. sovereignty, is ineffective in prosecuting war crimes and too often targets American allies, such as Israel.

The State Department also announced it is shuttering the Palestine Liberation Organization's (PLO) Washington office over concerns that it is attempting to trigger an ICC investigation of the Jewish state.

"The United States will always stand with our friend and ally, Israel," Bolton said. "We will not allow the ICC, or any other organization, to constrain Israel’s right to self-defense."

Palestinian officials said the decision would not affect its plans to pursue an ICC investigation and accused the U.S. of unfairly favoring Israel in stalled efforts to restart Middle East peace talks.

"We reiterate that the rights of the Palestinian people are not for sale, that we will not succumb to U.S. threats and bullying," Palestinian diplomat Saeb Erekat said in a statement to news organizations in advance of the speech. "Accordingly, we continue to call upon the International Criminal Court to open its immediate investigation into Israeli crimes."

Monday's speech amounted to a coming out party for Bolton, who has played a mostly behind-the-scenes role since becoming President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE's national security adviser in April.

The remarks allowed Bolton, a noted hawk, to make his own public imprint on the administration's approach to foreign affairs. As a top State Department official, Bolton led former President George W. Bush's charge against the ICC in the early 2000s. On Monday, he said America's refusal to sign the treaty creating it "remains one of my proudest achievements."

Bolton said the renewed push against the court also fits into Trump's goal of putting the interests of Americans "above all else."

"This administration will fight back to protect American constitutionalism, our sovereignty, and our citizens," he said. "No committee of foreign nations will tell us how to govern ourselves and defend our freedom."

The chief prosecutor of the ICC requested last November to open a probe into alleged "crimes against humanity" committed in Afghanistan by U.S. military and intelligence personnel.

Bolton said if the investigation moves forward, the U.S. would ban ICC judges and prosecutors from entering the U.S., sanction any funds they have in the U.S. financial system and even weigh criminal probes against them.

The administration will also pursue more "binding, bilateral agreements" to prevent other countries from handing over Americans to the ICC. Roughly 100 agreements already exist, according to Bolton.

The U.S. could also reconsider foreign aid to countries that participate in the ICC, a group that includes some NATO allies. Speaking to reporters after the speech, Bolton said such a review is "entirely appropriate" but stopped short of directly threatening aid payments.

"We will not cooperate with the ICC. We will provide no assistance to the ICC. And we certainly will not join the ICC," Bolton said, prompting applause. "We will let the ICC die on its own. After all, for all intents and purposes, the ICC is already dead to us."

The ICC was formed in 2002 to prosecute war crimes, genocide and crimes against humanity. But it has been shrouded in controversy from the start.

Bush refused to ratify the Rome Statute which led to its creation and his administration negotiated several dozen agreements with other nations designed to shield Americans from prosecution.

U.S. opposition to the court softened after Bolton left the Bush administration and under former President Obama, the U.S. took steps to cooperate with the body, such a providing assistance with investigations into alleged African war crimes.

Bolton appears determined to once again harden America's posture toward the ICC, saying it was unfit to investigate any allegation of war crimes or genocide worldwide, even in areas like Darfur or Syria.

"It is the wrong venue across the board," he told reporters.

If the Trump administration follows through with its threats against the court, it could raise questions about its legitimacy and provide cover for other countries, such as South Africa, that are considering exiting.

But if the ICC continues with its Afghanistan probe, it could improve its standing among skeptics who believe it is unwilling to pursue cases against major world powers.

Human-rights groups said the decision to take a hostile stance toward the ICC could further isolate the U.S. on the world stage.

"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.

Updated at 2:11 p.m.