The US Treasury Department has sanctioned International Criminal Court President Tomoko Akane and a senior lawyer at the court, according to Reuters. Secretary of State Marco Rubio announced the measures, CNN reported, calling them part of an effort to target the court's leadership.

The Trump administration has vowed to dismantle the ICC "brick by brick," according to the BBC. Sanctioning a sitting ICC president is a new step in that campaign, moving beyond the prosecutors and staff it has previously targeted to the court's top office.

The ICC is the only permanent tribunal that prosecutes genocide, crimes against humanity and war crimes when national courts do not act. Most of Washington's European allies are ICC members and back its independence, so sanctioning its president risks a rupture with allies who see the court as central to the international justice system the US helped build.

The precise scope of the sanctions is unconfirmed, as is how the ICC's roughly 120-plus member states, including the UK and EU, will respond — the next thing to watch.