THE group of 53 African states at the United Nations have publicly endorsed Secretary General Kofi Annan for a second term in office and asked him to declare his candidacy. Diplomats said Annan was so popular that if he decided to seek re-election before his five-year term expires on December 31, it would probably preclude the possibility of an Asian candidate. Traditionally, the post of UN secretary general has rotated among the world body’s four geographical groups, with each office-holder limited to two terms.