Talks to end the conflict in Iraq's holy city of Najaf collapsed today, raising the prospect of renewed fighting between US troops and radical Shi'ite militiamen challenging the country's interim government.
Interim Prime Minister Mr Iyad Allawi's government vowed an immediate resumption of a military crackdown in Najaf, where Iraqi troops have coordinated with US forces against militants supporting Shi'ite cleric Moqtada al-Sadr.
Iraq's national security adviser Mr Mowaffaq al-Rubaie said the Najaf talks had failed and a Sadr spokesman blamed the breakdown on Mr Allawi.
"The talks have failed. All efforts to end this have not succeeded," Mr Rubaie told reporters.
"The Iraqi interim government is resuming military clearing operations to...establish law and order in the holy city," he told a news conference.
Militants loyal to Sadr have been battling US and Iraqi forces in the sacred city of Najaf for ten days in fighting that has killed hundreds and sent thousands of protesters onto the streets.
A truce had held since yesterday but the collapse of the talks threatened a return to violence. Sadr has vowed a fight to the death to defend the holy city.
"You have to know, we had agreed with Rubaie on all points but Allawi called him back and he ended the issue," a spokesman for Sadr told the Arabic-language Al Jazeera television.
The collapse of the talks came on the eve of a national conference aimed at advancing Iraq's progress towards democracy, already overshadowed by the Shi'ite Muslim uprising.
The surge in fighting has proved the most serious challenge for Mr Allawi since his government assumed power from US occupiers on June 28th, tasked with steering the country to elections in January 2005.
The national conference aims to pick a 100-member council to oversee the government after it opens in Baghdad tomorrow.
Elsewhere in Iraq, US forces said they killed about 50 militants near the northern Iraqi town of Samarra today, a mainly Sunni Muslim area where US troops have launched repeated raids to flush out guerrillas opposed to the presence of foreign troops in Iraq.
Warplanes screaming overhead dropped 500-lb (225 kg) bombs, while insurgents responded with rifle fire and rocket-propelled grenades, a US military statement said, adding there were no US casualties.
Casting doubt on the US toll, Iraqi police in Samarra said at least five people had been killed and 50 wounded in fighting in the area, 100 km (60 miles) north of Baghdad.
Fighting also raged between US troops and Sadr followers in the southern Shi'ite town of Hilla overnight. Forty fighters and three police were killed, Iraq's interior ministry said, although the health ministry said 10 people were killed.
Before yesterday's truce in Najaf, US marines backed by tanks had launched an assault on Thursday to crush a rebellion by Sadr's fighters, based around the Imam Ali Mosque and a nearby vast cemetery.