President Donald Trump has imposed sanctions on court officials who are investigating whether US forces committed war crimes in Afghanistan.
In an executive order, Trump said the United States would block all US property and assets of anyone in the Hague-based tribunal involved in probing or prosecuting US troops.
Secretary of State Mike Pompeo said in a statement: "We cannot - we will not stand by as our people are threatened by a kangaroo court."
"I have a message to many close allies around the world -- your people could be next, especially those from NATO countries who fought terrorism in Afghanistan right alongside of us."
The ICC investigation began after a preliminary report found reason to believe war crimes had been committed.
Mr Trump has repeatedly criticised the court and questioned its independence.
The US is not a signatory of the Hague-based ICC and does not recognise its authority over American citizens.
His criticism of the court was compounded by Attorney General William Barr, who alleged without evidence that "foreign powers like Russia are manipulating the ICC in pursuit of their own agenda".
Barr said that the administration was trying to bring accountability to an international institution.
"This institution has become, in practice, little more than a political tool employed by unaccountable international elites," he said.
Human Rights Watch said that Trump's order "demonstrates contempt for the global rule of law."
"This assault on the ICC is an effort to block victims of serious crimes whether in Afghanistan, Israel or Palestine from seeing justice," said the group's Washington director, Andrea Prasow.
"Countries that support international justice should publicly oppose this blatant attempt at obstruction," she added.
Trump has been tearing down global institutions he sees as hindering his administration's interests, recently ordering a pullout from the World Health Organization over its coronavirus response.
The investigation into alleged war crimes by the US and others in the Afghan conflict was given the green light by the ICC earlier this year.
The actions of the Taliban, the Afghan government and US troops since May 2003 are expected to be examined in the probe.
Afghanistan is a member of the court, but officials there have also expressed opposition to the inquiry.
The administration last year revoked the US visa of the court's chief prosecutor, Gambian-born Fatou Bensouda, to demand that she end the Afghanistan probe.
But judges in March said the investigation could go ahead, overturning an initial rejection of Bensouda's request.
In April 2019, a pre-trial chamber at the ICC ruled that the investigation should not go ahead because it would not "serve the interests of justice".
Founded in 2002, the International Criminal Court was set up with a mission to investigate war crimes, crimes against humanity and genocide.
But it immediately ran into opposition from Washington, where the then administration of George W. Bush actively encouraged countries to shun the court.
President Barack Obama took a more cooperative approach with the court but the United States remained outside of it.