Threats by the United States to sanction judges from the International Criminal Court if it pushes ahead with a probe into war crimes in Afghanistan have further strained Washington's relationship with the tribunal.
Here are four questions and answers about The Hague-based ICC:
- What does the ICC do? -
The International Criminal Court was created through the adoption of its founding Rome Statute in July 1998 and started operating in The Hague in July 2002.
To date 123 countries have signed up to the court, which has a mandate to investigate and prosecute the world's worst crimes including genocide, war crimes and crimes against humanity. It is the world's first permanent war crimes court.
An independent legal institution, the ICC is a court of last resort and can only get involved when states are unwilling or unable to investigate the crimes themselves.
The United States is one of the few Western countries that has not joined. Although it did sign the Rome Statute, it was never ratified under the administration of former president George W. Bush.
China, Israel and Russia have also not ratified the statute.
- Can the ICC probe US citizens? -
In Afghanistan it can. The Rome Statute says the ICC can exercise its jurisdiction to probe crimes where "one or more" states have signed up to the treaty and the alleged crimes were committed on the territory of such a state.
Afghanistan joined the Rome Statute in February 2003, therefore the ICC's prosecutors argue they have jurisdiction to investigate any crimes committed in the war-ravaged country.
Following a preliminary probe, the ICC's chief prosecutor Fatou Bensouda in November last year asked the court's judges to authorise her to open a full-blown investigation into war crimes and crimes against humanity committed in Afghanistan, including by US forces and members of the CIA.
It is believed that a decision by the court's judges on the matter is imminent.
- What crimes? -
In 2007 the ICC said it was opening a preliminary investigation in Afghanistan reaching back to 2002, shortly after the United States launched Operation "Enduring Freedom" in the wake of the September 11 attacks.
The probe is also looking at war crimes committed by the Taliban and its affiliated Haqqani network as well as the Afghan National Security Forces.
But the ICC has particularly targeted CIA operations, saying information "provides a reasonable basis to believe members of the CIA committed war crimes of torture and cruel treatment, outrages on personal dignity and rape and other forms of sexual violence."
Euphemistically called "enhanced interrogation" these alleged crimes "appear to have been committed with particular cruelty, involving the infliction of serious physical and psychological injury... leaving victims deeply traumatised," Bensouda said.
- Can the US hit back? -
Inside US circles there have been different strands of thought as to how to engage with the ICC, said Carsten Stahn, international criminal law professor at Leiden University.
Under former president Barack Obama, the adminstration unofficially supported the ICC where it served US interests.
But "the pendulum has now shifted to a more aggressive policy," Stahn told AFP.
National Security Advisor John Bolton said on Monday the US was prepared to slap financial sanctions and criminal charges on ICC officials if they proceeded against any Americans.
But Stahn said such a move would be unprecedented, adding that "experts dispute whether such a claim has a basis in US law."
The US Congress in 2002 passed the American Service Members Protection Act which contained a number of provisions should a US citizen ever be dragged before the world war crimes court.
Also known as the "Hague Invasion Act," one provision within the federal law allows for the US president to authorise military force to free any US personnel held by the ICC.
However, "threatening to remove ICC detainees by force would be a clear violation of international law," Stahn said.