Members of the International Criminal Court (ICC) will meet in Uganda next week to discuss a possible expansion of the court's powers allowing it to prosecute crimes of state aggression.

The ICC is the first permanent international court that can try individuals for genocide, war crimes and crimes against humanity. But from Monday, delegates from 111 member states will seek agreement in Kampala on how to define state aggression, one of four crimes over which the ICC has jurisdiction but one which it has yet to tackle, in part because of political sensitivities.

A deal could open the door for the court to prosecute crimes such as the invasion of another country, a port blockade or a state allowing another nation to use its territory to wage war on a third state.

"This would be both a significant step forward in the development of international law and an important extension of the court's jurisdiction," Christian Wenaweser, president of the Assembly of States Parties (ASP), said on Thursday in a live blogging session hosted by the court.

Wenaweser said there was agreement that the UN Security Council should be the first body to determine whether state aggression - using force manifestly contrary to the UN charter - had taken place, but the council's role still needs to be fully defined.

Human Rights Watch has warned that allowing the Security Council to decide on ICC probes into state aggression would undermine its judicial independence. It also cautioned that the new powers could suck the court into politicised disputes between states.

The first prosecutor of the International Criminal Tribunal for the former Yugoslavia (ICTY), Richard Goldstone, said in an opinion piece in the New York Times earlier this week that now was "not the time" to add the crime of aggression to the court's powers, as it would arm critics of the ICC who accuse it of being a politicised institution.

In addition to finding a consensus on the definition of the crime of aggression, the member states will discuss conditions for the ICC to exercise jurisdiction and on how to apprehend its suspects. The court relies on governments to carry out arrests, but seven suspects are still at large.

The ICC members will also take stock of the achievements of the Hague-based court , which opened its doors in 2002 and started its first trial in January 2009 against Congolese warlord Thomas Lubanga Dyilo, overcoming early delays. A second trial against two other militiamen from the Democratic Republic of Congo is ongoing while a third trial - against former Congolese vice-president Jean Pierre Bemba is due to begin in July.

Amnesty International in its annual report published this week says governments are blocking progress on human rights by refusing to join the ICC or by shielding allies from justice. It urged states, particularly G20 nations, to fully sign up to the ICC.