Humanitarian organisations are preparing to launch a fundraising appeal for $500 million (454 million euros) for the crisis created by the Islamic State group in Iraq, UNICEF said on Monday.
The announcement came a day ahead of a meeting in Paris of the US-led coalition of countries working to defeat the jihadist group in Iraq and Syria.
"The humanitarian situation in Iraq is close to disaster! We urgently need extra resources," Philippe Heffinck, UNICEF's representative in Iraq, said in a statement in French.
"500 million is really the bare minimum. We're cutting it down to the bare bone," he added in later comments to AFP.
According to the UN children's agency, eight million Iraqis are in urgent need of humanitarian aid, in particular the roughly three million people who have been forced to flee their homes since the start of the IS offensive in June 2014.
"We expect that this will increase by one million more by the end of the year," predicted Heffinck.
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Access, however, has been hampered by the fighting and a lack of funding is now even threatening such humanitarian assistance as has been possible, UNICEF said.
As a result, all those organisations currently operating in Iraq will in Brussels on Thursday launch "a fundraising appeal for nearly $500 million to cover relief operations over the next six months", the agency added.
"We hope that all the countries, western and neighbouring, will respond. The situation is too desperate," stressed Heffinck.
"If we don't do it now, we are going to have a major disaster that will cost much more to the international community," he added.
The US-led coalition of some 60 nations was formed last year after IS went on a rampage across Iraq and Syria, seizing key territory and declaring a caliphate.
Ministers from Turkey, Saudi Arabia, Qatar, and the United Arab Emirates are expected to be among 24 participants attending the anti-IS coalition meeting in Paris.
The main focus of the meeting will be the situation in Iraq, where IS seized the city of Ramadi two weeks ago in the biggest blow to the coalition since it began bombarding jihadist positions in August.