Indicting President Omar al-Bashir of Sudan over alleged war crimes in Darfur could put peacekeepers at risk, a senior UN official has warned.
Assistant Secretary-General for Peacekeeping Edmond Mulet also said an arrest warrant against Mr Bashir could derail Sudan's north-south peace deal.
The International Criminal Court's chief prosecutor sought a warrant against President Bashir in July.
Mr Bashir rejects the allegations and has lobbied to delay the investigation.
Judges have asked ICC chief prosecutor Luis Moreno Ocampo to provide more evidence before they decide whether to issue a warrant.
Mr Mulet told the UN Security Council that peacekeepers from a joint African Union-UN force could be expelled from Darfur if such a warrant was issued.
He also said a separate UN peacekeeping force, UNMIS, in semi-autonomous South Sudan could be targeted.
"We are concerned about suggestions of an uncontrolled reaction to an indictment by the population against UNMIS," he said.
Mr Mulet also said an indictment could "potentially derail" the 2005 peace process that ended more than two decades of civil war between northern and southern Sudan.
In Darfur, the UN estimates that up to 2.7 million people have been forced from their homes and some 300,000 have died during five years of conflict.
Mr Moreno Ocampo has said there were grounds to believe Sudan's president bore criminal responsibility on 10 counts of genocide, crimes against humanity and war crimes.
Sudan's government has always denied charges that it armed the Janjaweed militias accused of widespread atrocities against civilians in Darfur.
The African Union and Arab League have backed Sudan in its opposition to any indictment of Mr Bashir.