Disagreement between Nato and the European Union has stymied arrangements for the airlift of thousands of African Union troops to Sudan's stricken province of Darfur, weeks before the mission is set to begin.

Last week, George W. Bush, US president, promised to support the AU observation mission in Darfur, where the United Nations has estimated at least 180,000 people have died. The AU plans to increase its troops from about 2,500 to 7,700 by September.