GENEVA, April 8 (Reuters) - The United Nations human rights investigator for Sudan has demanded that the government disarm militia who continue to kill and rape civilians in Darfur, warning of a "time bomb" that could explode.

Emmanuel Akwei Addo, the independent U.N. expert on the situation of human rights in the Sudan, said on Friday that 2,000 African Union troops lacked power to deter crimes in the remote region where aid workers were pulling back due to deteriorating security.

The United States and European Union (EU) echoed his alarm and called for action by the U.N. Commission on Human Rights, holding its annual session through April 22.

Officials from African countries and the EU are negotiating the text of a joint resolution which could be put to a vote by the 53-member state forum next week, according to diplomats.

"The present situation in Darfur is said to be a time bomb, which could explode at any moment," Addo told the Geneva forum.

"The rebels have grown more intransigent, and security on the ground is getting worse ... Aerial bombardment still goes on," he said.

Addo said there were strong indications that Janjaweed militia and government forces had committed "war crimes" and "crimes against humanity" in Darfur, including murder, torture, rape, and forced displacement.

"RUTHLESS CAMPAIGN"

The Khartoum government, which had responsibility to protect all citizens, had ignored repeated demands to disarm the militia who are waging a ruthless campaign in near total impunity, according to Addo, a justice from Ghana.

Tens of thousands have been killed and more than 2 million people have fled their homes in Darfur since a rebellion broke out in early 2003.

Khartoum retaliated by arming nomadic Arab militia known as Janjaweed, who are accused of waging a campaign against black African villagers which the United States has called genocide.

The U.S. delegation called Darfur "the most egregious example of human rights abuse in the world at this moment".

Sudan "must accept its responsibility, cease attacks on innocent civilians and implement its obligation to disarm and disband the Janjaweed," said U.S. Ambassador Rudy Boschwitz, a former senator from Minnesota who heads the U.S. delegation.

"This commission can help by going unequivocally on the record with the strongest possible resolution that accurately documents the situation in Darfur," he added.

Luxembourg, speaking on behalf of the 25-member EU, said that the situation in Darfur was "alarming".

It was fundamental to the Commission's credibility that it voice international concern "in the clearest possible manner", Luxembourg's ambassador Alphonse Berns said in an EU statement.