With proven oil reserves of around 112 billion barrels and up to another 150 billion barrels of probable reserves, Iraq is the greatest untapped prize for international oil companies.

To put that in context, if Iraq does turn out to have around 300 billion barrels of oil, it will rival the world's biggest producer Saudi Arabia - which has around 160 billion barrels of proven reserves.

So it is little wonder that giant international oil companies are lining up to get back into Iraq after the industry was nationalised in the 1970s and the oil majors were kicked out.

On June 30 major companies - including Exxon, Shell, BP and Total - will gather at Iraq's oil ministry in Baghdad for a two-day meeting to take part in the first bidding round for oil service contracts.