(Updates with background) BAGHDAD, Dec 16 (Reuters) - Iraqi Prime Minister Nuri al-Maliki said on Saturday Iraqi army officers of all ranks sacked after the U.S. invasion in 2003 would be allowed to reapply for their posts in the new army. The Shi'ite premier issued the invitation, a gesture towards disgruntled minority Sunnis, at a national reconciliation conference in Baghdad aimed at easing sectarian violence that U.N. officials estimate causes more than 100 deaths a day. Shortly after the U.S. invasion to topple Saddam Hussein, U.S. administrator Paul Bremer quickly dissolved the Iraqi army, a decision experts consider a miscalculation. Many of its members then joined the ranks of the Sunni insurgency. The Defence Ministry has recruited former officers of Saddam's army in the past but limited the invitation to junior ranks. Maliki's invitation was the first extended to all ranks. "The new Iraqi army is opening the door to former Iraqi army officers. Those who do not come back will be given pensions," he told a conference of Kurdish, Sunni Arab, Shi'ite and secular politicians. The U.S. military has been training the new, 300,000-strong army as part of a plan eventually to withdraw its own 135,000 troops. Sunnis view the Shi'ite-dominated army with suspicion and there are doubts about its sectarian loyalties. Bremer, who governed Iraq for 13 months after Saddam was removed, has said it is not fair to criticise him for disbanding the Iraqi military, which reversed plans by Jay Garner, his predecessor, to use it to help rebuild the country. Saddam had used the military to reinforce his hold on power, but some experts argue that former members of the disbanded army, suddenly jobless, went on to help form the insurgency. Bremer says the final decision lay with Washington, which approved his recommendation. Supporters of the decision said the military had effectively disbanded itself with thousands deserting in the face of the U.S.-led invasion.