Three US soldiers have been killed in Iraq's Najaf province, scene of clashes between occupation forces and Shia Muslim fighters, amid fresh efforts to stop the fighting. "Three US soldiers attached to the 11th Marine Expeditionary Unit were killed as a result of enemy action in Najaf province 15 August," said a US military statement, issued on Monday. Thick smoke rose from Najaf on Monday morning before an expected major military assault on Shia leader Muqtada al-Sadr's al-Mahdi army fighters. "There is thick smoke rising from the city, but there is no gunfire or explosions. The city is quiet," an AFP correspondent said. Meanwhile, Iraq's national conference is to send a delegation to urge Muqtada al-Sadr to withdraw his fighters from Najaf and turn his al-Mahdi army into a political party. Participants approved by a show of hands the proposal put forward by a relative of al-Sadr, Baghdad Shia cleric Shaikh Husain al-Sadr, who told the conference on Monday: "There are inviolable conditions in civilised countries, particularly that there is no place for armed militias." **Three-point plan*** "I suggest you appeal urgently to Muqtada al-Sadr as we did yesterday to the Iraqi government and draw up a three-point resolution that everyone can agree with. "Firstly, that the al-Mahdi army withdraw from the shrine, that (they) renounce weapons and become a political party," he added. The text was approved by a show of hands, but certain al-Sadr sympathizers complained against the method of voting and one said he would leave the conference. Khodair al-Abbas, from the Shia Dawa party of Vice President Ibrahim Jafaari, said his party fully supported the initiative and that a delegation from the national conference was being selected to deliver it to al-Sadr. In Najaf, a spokesman for al-Sadr, Shaikh Ahmad al-Shaibani, said the question of the militia laying down arms and becoming a political organisation could only be solved by "negotiations and not a unilateral decision". **Sporadic clashes*** "We can come to an agreement on this through negotiations. We are ready to defend ourselves as we are ready for peace," he said. Sporadic fighting occurred in Najaf on Sunday after a two-day truce following a week of clashes ended with the breakdown of negotiations between al-Sadr and the Iraqi government. "A major assault by forces will be launched quickly to bring the Najaf fight to an end," Interior Ministry spokesman Sabah Kadhim said late on Sunday. "This matter has to be brought to conclusion as fast as possible and we want to bring the situation to normalcy soon," he added. Also on Sunday, foreign and Iraqi journalists and cameramen were ordered out of Najaf by local police, as authorities said their safety could not be guaranteed. The al-Mahdi army is in control of the mausoleum of Imam Ali - one of the holiest sites in Islam - in the centre of the old city, and parts of a vast cemetery nearby. **PHOTO CAPTION*** Mahdi army soldiers loyal to Shiite cleric Muqtada al-Sadr aim towards the direction of American tanks as they take positions near Najaf's sprawling cemetery in Najaf Monday Aug. 16, 2004. (AP)