Humanitarian groups have been preparing for months for a crisis of massive proportions. As the allied war machine slams into Iraq, they are putting their plans into practice. The potential for a human catastrophe is enormous. Most Iraqis rely on a heavily centralised infrastructure for their everyday needs and this will disintegrate rapidly. Conservative estimates indicate that almost 10 million people just under half of Iraq's population will be affected. Two million are expected to become refugees, adding to the one to two million already forced to live outside their country, with another 700,000 to one million people internally displaced. Under international law, if the US and its allies establish military control after Saddam Hussein falls, they will have responsibility for the humanitarian and security needs of Iraq's people in and outside the country. It will be an enormous and costly obligation. Iraq's 22 million people are already vulnerableafter 12 years of United Nations-imposed sanctions. In 1996, the UN began its controversial oil-for-food programme, under which Iraq could sell limited quantities of oil to buy food, medicine and other essential supplies. The result has been shortages and supply delays which have badly affected infrastructure. Water, sewage and electricity systems have become dilapidated due to a lack of spare parts. About 70 per cent of the population have depended on government rations, which are carbohydrate-based and comprise flour, rice, sugar, oil, tea, soap and washing powder. Military action has hit the flow of these rations, caused disruption to electricity and water shortages. The most vulnerable people are in the central and southern regions, where tens of thousands are dependent on government handouts, the US-based group Human Rights Watch said in a recent report. They would face immediate water and food shortages and be forced to move elsewhere to survive. With the American objective being the overthrow of Mr Hussein and the destruction of his alleged chemical, biological and nuclear weapons stocks, large numbers of people would also flee cities such as Baghdad and Basra to avoid the fighting. Even greater problems will occur at Iraq's borders with Iran, Jordan and Syria, which have sent mixed signals on taking large numbers of refugees. Some refugee camps have been set up in Iran and a steady trickle of fleeing people are crossing into Jordan. But Syria has still not formally said if it will allow in refugees. Iran already has the world's largest refugee population two million Afghans and about 300,000 Iraqis as a result of the stand-off with Iraq and more than two decades of unrest in Afghanistan. Several thousand more Iraqis are in Jordan and 5,200 live in a camp in Saudi Arabia. Turkey has indicated it is prepared for an influx of 100,000 displaced Iraqis into the insurgency-hit Kurdish southeast of the country. The Turkish Red Cross has estimated that at least US$50 million will be needed each month to cope with refugees alone. The UN High Commissioner for Refugees is co-ordinating emergency efforts to help neighbouring governments deal with the impending crisis. It maintains a stockpile in Denmark of essential equipment including plastic tarpaulins, jerry cans and buckets to cope with a disaster affecting up to 250,000 people. As during the war in Kosovo, daily rations of ready-to-eat meals similar to those used by the US military can be flown in. These are expensive and used only in extreme emergencies. Humanitarian groups such as CARE International, the Red Cross and Save the Children Fund will help people within Iraq. Each focuses on a specific emergency effort, such as displaced people in northern Iraq in the case of Save the Children Fund. These groups have for months been urging the US and its allies not to take the military option. A joint statement signed by Save the Children, CARE International, Christian Aid, CAFOD, Tearfund, Help Age International, Islamic Relief and 4Rs warned last month that a new conflict in Iraq risked ''deepening and extending the current humanitarian crisis, creating large numbers of civilian casualties and extending human suffering''. It said: ''Years of war and sanctions have already created an extremely vulnerable population whose ability to cope with any additional hardship is very limited. This includes children, who make up almost half of Iraqi society, widows, the elderly and the poor.'' Extensive and prolonged conflict risked undermining the essential supply of food and medicine and infrastructure, the groups warned. Nonetheless, they havebeen ensuring that hospitals have access to water and that emergency drugs are available. CARE International's Iraq representative, Margaret Hassan, described the situation as much different from 1991, when Iraqis still had a cushion of cash and supplies. The UN sanctions had severely eroded this safety net and many people were now poor and dependent on the government for food and health care, she said. ''The infrastructure, which was very sophisticated and therefore required lots of sophisticated spare parts and money to maintain, has not been kept as it was prior to 1990 as there isn't the money to do so.''