(Reuters) - Members of the International Criminal Court (ICC) will meet next week in Uganda to discuss a controversial expansion of the court's powers that would allow it to prosecute crimes of state aggression for the first time.

Delegates from 111 member states will seek agreement during a 10-day conference in Kampala on how to define state aggression, one of four grave 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, said Thursday.

In a live blogging session hosted by the court, Wenaweser said there was a "good basis for a solution that finds very wide political support."

In addition to finding a consensus on the definition of state aggression, the member states must agree conditions for the ICC to exercise jurisdiction and ways to modify the treaty which set up the court.

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

Human Rights Watch has warned 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 politicized disputes between states.

A former prosecutor at the Yugoslavia war crimes tribunal, Richard Goldstone, said in an opinion piece in the New York Times 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 politicized institution.

POLITICAL CONCERNS

The United States, which will attend the conference as an observer, is wary of politically driven prosecutions and has said if the crime of state aggression is added to ICC powers, jurisdiction should hinge on a Security Council determination.

In addition to the U.S., which withdrew its support for the ICC under then president George W. Bush in 2002, other Security Council powers China and Russia are not members of the ICC and cannot vote on the state aggression issue at the conference.

About 80 of the court's 111 member states have indicated they will attend the Kampala conference, to be joined by delegates from non-member states, the United Nations and more than 1,000 participants from non-government organizations.

Besides discussing the issue of state aggression, they will also take stock of the achievements of the Hague-based ICC, which was set up in 2002 and started its first trial in January 2009, overcoming early delays. A third trial is due to begin in July.

But Amnesty International 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. [ID:nLDE64P2EM]

The ICC relies on governments to carry out arrests, but seven suspects are still at large.

"We will be listening in Kampala for pledges of increased support to place perpetrators and would-be perpetrators on notice that they will be held to account," said Richard Dicker, international justice director at Human Rights Watch.

http://www.reuters.com/article/2010/05/27/us-warcrimes-icc-conference-idUSTRE64Q5KY20100527