UNITED NATIONS, Sept 22( Reuters)-Somalia has asked the United Nations to pause a planned drawdown of 3, 000 African Union peacekeepers for three months to allow its security forces time to regroup after a militant attack forced them to withdraw from several recently captured towns. The African Union Transition Mission in Somalia( ATMIS), which is mandated by the U.N. Security Council, took over from another AU mission in April last year.On June 30 ATMIS concluded the first phase of the drawdown