United Nations ? The chief prosecutor of the International Criminal Court will seek an arrest warrant Monday for Sudanese President Omar Hassan al-Bashir, charging him with genocide and crimes against humanity in the orchestration of a campaign of violence that led to the deaths of hundreds of thousands of civilians in the nation’s Darfur region, during the past five years, according to U.N. officials and diplomats.

The action by the prosecutor, Luis Moreno-Ocampo of Argentina, will mark the first time that the tribunal in The Hague charges a sitting head of state with such crimes, and represents a major step by the court to implicate the highest levels of the Sudanese government for the atrocities in Darfur.

Some U.N. officials raised concerns Thursday that the decision would complicate the peace process in Darfur, possibly triggering a military response by Sudanese forces or proxies against the nearly 10,000 U.N. and African Union peacekeepers located there. At least seven peacekeepers were killed and 22 were injured Tuesday during an ambush by a well-organized and unidentified armed group.

Sudan’s U.N. Ambassador Abdalmahmood Abdalhaleem Mohamad said that rebels are responsible for the attack on U.N. peacekeepers.