The EU's diplomatic chief on Thursday voiced "serious concern" at moves by President Donald Trump to sanction any International Criminal Court officials who investigate US troops.
Ramping up pressure for the Hague-based court to stop its probe of alleged war crimes in Afghanistan, Trump issued an executive order to block all US property and assets of anyone involved in probing or prosecuting American forces.
"For sure this is a matter of serious concern because we as the European Union are steadfast supporters of the International Criminal Court," EU foreign affairs high representative Josep Borrell told reporters.
"The court has been playing a key role in providing international justice and addressing the gravest international crimes -- it is a key factor in bringing justice and peace. It must be respected and supported by all nations."
Borrell said he would study Trump's order further to assess its implications, and the matter may be discussed by EU foreign ministers when they hold video talks on Monday.
Washington has never accepted the jurisdiction of the ICC and Secretary of State Mike Pompeo said the Trump administration would not let US forces be "threatened by a kangaroo court".
