"The International Criminal Court (ICC) just wants to prove itself at the cost of peace, and they seem not to care," leading mediator Betty Bigombe told Reuters.
"I have told the prosecutor that the moment they issue arrest warrants, I will stop the peace process."
Bigombe, a former Ugandan government minister, has been instrumental in making contact with the cult-like LRA, which has never given a clear account of its political aims.
The surrender this month of two senior LRA officers, which followed the first face-to-face talks with the government for a decade, raised hopes more rebels might leave the bush and accept a long-standing government amnesty.
But a handful of LRA officers could face indictments this year following an ICC investigation. Held hostage by the commanders, aid workers say, are some 700 youngsters forced to serve the group as fighters, porters and sex slaves.
The ICC is backed by almost 100 countries, but not by the United States, which fears it could be used to target American troops serving abroad. It can only prosecute crimes committed since it was set up in 2002, and has so far focused on Africa.