THE United States has invited African energy ministers to a conference next month where it hopes to draft a coordinated strategy for energy development on the continent while promoting US businesses there, US Energy Secretary Bill Richardson said in Washington on Monday. Already 35 of 54 African ministers have agreed to attend the gathering December 13-15 in Tucson, Arizona. Describing Africa as “the next untapped resource of the world,” Richardson said the conference would debate strategies to encourage investment aimed at ensuring sustainable energy development there.