IT was George Bernard Shaw who described Britain and America as two nations divided by a common language. He certainly had a lasting point. Today, Prime Minister Tony Blair and US Secretary of State Colin Powell are two men, a Briton and an American, divided by their common language. There is a very important word whose meaning they cannot agree upon. The word is sovereignty. They both use it in the same context - Iraq - but clearly believe it means different things. For Mr Blair, it means that when the interim government takes over in Iraq at the end of this month it will enjoy full sovereignty, including the right to approve military operations undertaken by the US, UK and other national forces that will remain in Iraq. Mr Powell, however, has said several times that the US Army will retain its operational independence after 1 July although it will consult with the interim government as necessary. On Wednesday he spelt this out again: the Iraq interim government will have no veto over the activities of the multi-national coalition force led by the United States. It is hardly surprising, therefore, that the US/UK draft resolution on Iraq's future being considered by the UN Security Council contains no reference to the relationship between the Iraq interim government and the multi-national force. Jack Straw, the British Foreign Secretary, said yesterday that this matter would be dealt with by a separate Letter of Agreement between the US/UK and the Iraqis. But it is unlikely that China, France and Germany will agree with that evasion of Security Council authority. A new resolution is essential to Iraq's future so it cannot be one that permits any uncertainty about the precise meaning of the word sovereignty.