Among the 10 million Iraqis requiring urgent assistance are more than 3.3 million people displaced by the conflict with Islamic State since 2014 and a quarter million people from neighboring Syria who have fled from their country's nearly five-year-old war, according to the United Nations. Children make up half of the displaced population.
The Iraqi government allocated around US$850 million last year for efforts to shelter such families and help them return to recaptured areas, but it ended up funding less than 60% of that, according to a government report.
The UN plan said it was only asking for a fraction of the US$4.5 billion deemed necessary to meet humanitarian needs in an acknowledgment of security and funding constraints on its operations.
Islamic State seized about a third of Iraq's territory in the north and west in 2014, but has slowly been pushed back by Iraqi forces, Iranian-backed Shi'ite militias and Kurdish peshmerga fighters - backed by US-led coalition air strikes.
Most of the displaced people, living in makeshift camps, disused buildings and homes in Baghdad, the northern Kurdistan region and other areas, are from Iraq's Sunni minority.
Jaff said he expected 200,000 families could return home this year.