The formal selection of the electoral commission came three days after the appointment of an interim government in a process overseen by Washington with UN participation.

The new government told the United Nations it wanted the right to decide on the future presence of US-led forces and other security issues but in general sided with Washington.

The United States is trying to persuade other major powers, including France and Russia, to support a UN mandate to keep US-led troops in Iraq until the country has a fully legitimate, constitutionally elected government -- scheduled for about 18 months time in the current US transition plan.

Foreign Minister Hoshiyar Zebari told the UN Security Council in New York that Baghdad wanted US-led forces to stay, under the terms of a US-British draft resolution on the planned US handover of power to Iraqis on June 30.

Officials in Baghdad said proportional representation would be used to elect an assembly that will oversee the drafting of a new constitution and choose a replacement for the present interim government.

Much of the voting is likely to be along the lines of Iraq's ethnic and religious communities -- notably Shia and Sunni Muslim Arabs and the non-Arab Kurds in the north. The interim government, led by secular Shia Prime Minister Iyad Allawi, already reflects efforts to balance those groups.

"I stress that any premature departure of international troops would lead to chaos and the real possibility of a civil war in Iraq," Zebari said.

The biggest threat to holding elections is violence that has afflicted the country since the US invasion 15 months ago.

One major seat of conflict, around the Iraqi holy city of Najaf, appears to be calming down.

Shia politicians said after hours of late-night talks in Najaf that militant cleric Moqtada al-Sadr had agreed to fresh measures to shore up a shaky truce and end weeks of fighting across the Shia south with US-led forces.

Friday morning was calm in the area, although Sadr supporters in Baghdad's poor Shia neighborhood of Sadr City burned down a police station and clashed with US troops.

Negotiators in Najaf said Sadr had agreed to withdraw his Mehdi Army fighters from the city within two days as long as US forces also withdrew, and had proposed neutral monitors.

Sadr announced last week he would pull his militiamen from Najaf and the nearby town of Kufa, and in return the US military said it would suspend offensive operations.