United Nations envoy Martin Kobler warned on Friday that Iraq is at a "crossroads," calling for restraint as a wave of violence killed more than 190 people in four days.
"I call on the conscience of all religious and political leaders not to let anger win over peace, and to use their wisdom, because the country is at a crossroads," Kobler said in a statement.
Kobler spoke a day after Prime Minister Nuri al-Maliki warned that the country was in danger of returning to "sectarian civil war."
Maliki, from Iraq's Shiite Muslim majority, called on people "to take the initiative, and not be silent about those who want to take the country back to sectarian civil war."
The country was torn by Sunni-Shiite fighting in 2007-2008 in which thousands of people were killed each month.
The latest trouble began on Tuesday when security forces moved in against anti-government protesters near the northern Sunni Arab town of Hawijah, sparking clashes that left 53 people dead.
Dozens more were killed in subsequent unrest, much of it linked to Tuesday's clashes, and the death toll had reached 195 by Friday.
The violence is the deadliest so far linked to demonstrations that broke out in Sunni areas of the country more than four months ago.
The protesters have called for the resignation of Maliki and railed against authorities for allegedly targeting their community.