'UN contingency planning envisages the arrival of 250,000-900,000 refugees from Iraq,' says a member of the humanitarian team in Tehran. 'But the situation is unpredictable and can change rapidly.'

Senior Iranian officials have voiced concern about both the size of the influx and the level of international assistance to help it cope with the crisis. Border crossings still remain closed, but are expected to be opened if there is a mass movement of Iraqis.

Iran's frequent natural disasters have made the IRCS one of the world's most experienced bodies in humanitarian crisis management. As well as coping with earthquakes, droughts, landslides and floods, it has also learned to deal with the overspill from conflicts in neighbouring countries. It has already set up camps along the border and the government is working with the UN on other forms of aid, including the provision of fresh water to Iraq.

The organisation is understood to have enough food and non-food aid to cope with the Iraq crisis alone, but is concerned that its emergency stocks will be severely depleted. So far, both Russia and Japan have made bilateral humanitarian donations to Iran through the IRCS.

Concerns that the US would prevent financial aid to an 'axis-of-evil' country have so far proved unfounded. Washington did stipulate that none of a $2 million donation it made to UNICEF should be channelled through Tehran, but is not expected to go further. 'Despite [US Defense Secretary Donald] Rumsfeld's outburst in the opening week of the war, it would appear that both the US and Iran want to maintain cordial relations so long as this crisis lasts,' says a UN official.

Any refugees hoping to reach Iran from Iraq will also face one of the most heavily mined borders in the world. The government says there is a strip of mined land 30 kilometres deep, running the length of its 1,500-kilometre border with Iraq. Because Iraqi forces laid many of these mines while they held Iranian territory in 1981-83, Tehran does not have accurate plans showing their deployment. Even the areas designated as refugee camps have only been cleared to military standards, with mines buried more than 20 centimetres underground remaining undetected.

However, a team of UN experts is now assembling in Iran to assess and improve the situation.