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The International Criminal Court (ICC) on Thursday hit back at a decision by US President Donald Trump to authorise sanctions against any official investigating American troops over alleged war crimes in Afghanistan.

Trump said earlier that the United States would block US property and assets of anyone from The Hague-based tribunal involved in probing or prosecuting US troops.

"These attacks constitute an escalation and an unacceptable attempt to interfere with the rule of law and the Court's judicial proceedings," the court said in a statement.

After a long-running legal process, the ICC said in March that an investigation into the Afghan war could go ahead.

The Trump administration has been livid over the possibility of a probe into atrocities in Afghanistan, America's longest-running war.

But the ICC said the "unprecedented" sanctions "undermine our common endeavour to fight impunity and to ensure accountability for mass atrocities".

The court added: "An attack on the ICC also represents an attack against the interests of victims of atrocity crimes, for many of whom the Court represents the last hope for justice."