The African Union has asked the U.N. Security Council for a resolution that would allow military intervention in Mali, where Islamist militants have become an international security threat, the union’s commission chief said on Tuesday.Jean Ping said union officials would meet Security Council representatives in New York to discuss the issue further, but he did not give any date for the meeting or details of proposed military aims in the West African state.Mali, once regarded as a good example of African democracy, collapsed into chaos after soldiers toppled the president in March, leaving a power vacuum that enabled Tuareg rebels from the north to take control of nearly two-thirds of the country.The uprising also involved both local and foreign Islamist militants, and Western diplomats talk of the risk of the country turning into a "West African Afghanistan”. Mali’s former colonial ruler France has six of its citizens held hostage in an unknown location in the region by al Qaeda’s north African arm.