By Joshua Rozenberg

This year, I am assured, the first defendants will stand trial at the world's only permanent international criminal court. There will be nobody in the dock - much to the disappointment of headline writers - because defendants will sit, American-style, alongside their lawyers. Guards will be stationed at the back of the court in case an alleged mass murderer makes a lunge for the three judges, seated alarmingly near by. One of those judges will almost certainly be Sir Adrian Fulford, a member of the English High Court who was to be found yesterday clocking up experience in the Court of Appeal. The windowless temporary courtroom, with its calming wooden panelling and strangely dissonant carpet tiles, has been built in the car park of a former office block in The Hague.

It will be a historic moment when the first defendants are brought up from the cells, though one that the United States seems to have done everything in its power to prevent. Who will those defendants be? Last October, the International Criminal Court announced that it had issued arrest warrants for leaders of the Lord's Resistance Army, the group of armed rebels that has been terrorising northern Uganda for the past 20 years. The rebels' commander, Joseph Kony, faces 12 counts of crimes against humanity and 21 counts of war crimes, including rape, murder, sexual enslavement and forced enlisting of children.

Before they can be tried, however, they must be found. The court is not part of the United Nations and has no police force of its own. Instead, it must rely on national law enforcement agencies, supported by the international community, to make arrests and send defendants to The Hague. Nobody knows how quickly Uganda's rebels will be brought to justice. But prosecutors are confident that trials will begin this year - not in the Uganda case, but in an entirely separate hearing involving the Democratic Republic of Congo.

After investigations by court staff into allegations of rape, torture, forced displacement and the illegal use of child soldiers in the country's lawless north-eastern Ituri region, Fatou Bensouda, one of the two deputy prosecutors at The Hague, expects "significant or substantive steps in the not too distant future".

Her boss, Luis Moreno Ocampo, was even more intriguing in an interview for The Court of Last Resort, a two-part series starting on Radio 4 on Monday. "I cannot explain to you why," he said, "but Congo will be the first trial." How can the chief prosecutor be so sure? He would not say. But it was reported recently that some of Congo's militia leaders had already been detained there. For all we know, Mr Moreno Ocampo may have issued secret "sealed" warrants for their arrest. If that proves to be the case, the first we will know about it is only after they have been flown secretly to The Hague.

One other conflict is under investigation by the prosecutor - the Darfur situation in Sudan, where both rebel militias and Sudanese government officials are accused of committing war crimes. When the UN Security Council decided last year to refer the Darfur case to the International Criminal Court, the US chose not to exercise its veto.

But a reference by the Security Council is not the only way that cases can come before the court. Any one of the 100 states that have ratified the Rome Statute can refer a situation to the court, as happened with Uganda and the Democratic Republic of Congo. The Central African Republic has also made a referral, but Mr Moreno Ocampo has not yet decided whether to open a formal investigation.

Crucially, however, the prosecutor has the power to initiate investigations on his own initiative. That's one of the reasons that the United States is not one of the court's 100 states parties. John Bellinger, legal adviser to the US State Department in Washington, told me that the Rome Statute of 1998, which set up the court, created an "unaccountable" prosecutor who could initiate "potentially politically motivated" cases on his own. "We felt that kind of unchecked power was a dangerous thing," he said. Mr Bellinger stressed that he was not casting aspersions on Mr Moreno Ocampo, "by all reports, an absolutely committed, upright and independent individual", but the prosecutor was not subject to any checks and balances from the Security Council.

It was curious to hear the US setting so much store by the UN. Other states at the court's founding conference in Rome in 1998 were less willing to involve the UN. Instead, the court's statute says the prosecutor cannot even begin a formal investigation on his own initiative without the approval of a "pre-trial chamber" of judges. States can object at this stage.

Mr Moreno Ocampo is currently monitoring eight "situations", but I suggested to Mr Bellinger that launching a case against the US, Britain or Europe was the last thing the prosecutor would do. "We have heard that argument before, and I certainly understand that neither the prosecutor nor the judges would want to damage its own reputation," Mr Bellinger said. But the checks and balances sought by his country in 1998 were simply not there. "It is unfortunate, frankly, that the world community left the US behind and did not address our concerns at the time."

At the heart of US opposition is the fear that its own troops will be hauled up before the International Criminal Court. Britain has immunised itself against that risk by taking power to bring war crimes prosecutions in its own courts. Why is Mr Bellinger so worried when Britain, its coalition partner, is a firm supporter of the court? "Perhaps we're being overly cautious, but I think not," Mr Bellinger said. There had been an "explosion of litigation" against government officials. As the country that made the greatest contribution to peace-keeping missions around the world, the US was most at risk.

Philippe Kirsch, the French-Canadian president of the court, has little time for such arguments. "This business about politically-motivated prosecutions, which is a motto that has been heard for years against the ICC, first of all is extremely difficult to substantiate on the basis of the legal requirements of the statute," he told me. "But also, it has received no substantiation in practice. In the past two and a half years that the court has existed, there is not a shred of evidence that the ICC has done anything of any political nature."

There are still some people who believe the court is politically motivated, I reminded Judge Kirsch. He shrugged. As cases proceeded, it would become clear "beyond any reasonable doubt" that the court was acting "exclusively judicially". And at some point, he was sure, "those arguments will collapse under their own weight". And would those "other countries" eventually withdraw their opposition and come on board? He was sure they would. "To me, it is not a matter of whether: it's a matter of when."