Uganda's government and the rebel Lord's Resistance Army signed the last in a series of documents paving the way for a peace agreement to end one of Africa's longest-running conflicts on Friday.

But the rebels refused to set a date for a final deal unless their leader Joseph Kony, who is thought to be hiding in the Democratic Republic of Congo's deep forests, is granted immunity from international prosecution.

"The arrest warrants issued by the Court against the LRA Commanders remain in effect and have to be executed," the office of ICC prosecutor Luis Moreno-Ocampo said in a statement.

The prosecutor declined to comment on the peace process and reiterated that it was up to ICC judges to rule on any challenge to the admissibility of the case against the LRA rebels.

The ICC was set up in 2002 as the world's first permanent court for trying individuals for war crimes. It is investigating crimes in the Democratic Republic of Congo, Sudan and the Central African Republic as well as Uganda.

The Uganda case highlights the challenge for the new court in balancing peace and justice, but Moreno-Ocampo has repeatedly insisted that trying those considered most responsible for human rights abuses is essential for lasting peace.

The Ugandan government has rejected a rebel demand for immunity for Kony before a final peace deal is signed but has said it will ask the U.N. Security Council to adopt a resolution requesting the ICC to defer the case against the LRA.

The two sides have also agreed to set up special war crimes courts in Uganda.

The ICC has indictments out on Kony as well as two of his deputies for crimes against humanity. The LRA has been accused of murder, rape, the abduction of children and slicing off body parts during 20 years of conflict.

Tens of thousands have been killed and some 2 million displaced from their homes in the conflict that has affected the Democratic Republic of Congo and Sudan as well as Uganda.