Athletics Kenya's chief executive has asked to step aside for 21 days pending an investigation into allegations he sought bribes to reduce the doping bans of two athletes who failed drugs tests, officials said Tuesday. AK officials showed journalists a letter that they said was from Isaac Mwangi that stated: "The allegations have caused me a lot of mental anguish ... I am anxious to have my name cleared." The letter, dated Monday, said Mwangi wanted to step aside to let the federation investigate allegations by athletes Joy Sakari and Francisca Koki Manunga that he asked each of them for $24,000 to reduce their four-year bans. "He hopes that this will vindicate him because he feels he is innocent," said the AK executive committee member. Mwangi last week dismissed the allegations against him as a "fabrication." AK's former president and two other senior officials are also currently being investigated by the IAAF on suspicion of corruption. These cases, coupled with a spate of failed drugs tests by its athletes over the past few years, have raised fears that Kenya could follow Russia in being suspended from international athletics. A member of the federation's executive committee said Mwangi had asked for an investigation into allegations by Joy Sakari and Francisca Koki Manunga that Mwangi had asked each athlete for $24,000 to reduce their four-year bans. Mwangi last week dismissed the allegations as a "fabrication." Athletics Kenya is due to hold a press conference in Kenyan capital Nairobi Tuesday afternoon. Russia orders athletes to sign anti-doping pledge All Russian athletes must sign an anti-doping declaration to take part in this month's national indoor athletics championships, the secretary general of the All-Russian Athletics Federation (ARAF) Mikhail Butov said Tuesday. "All the athletes who are going to compete at Russia's indoor championships in February need to sign the declaration," Butov told TASS state news agency. "Without their signature on the document, they will not be allowed to compete." The declaration has been recently drawn up by ARAF. The federation stated that athletes competing for Russia internationally and the team's support staff must all sign the document along with all the participants in the national championships. Those who have signed the declaration pledge never to use, transport, store or distribute the substances listed in the banned medications record. They have also to fulfill all the demands concerning dope testing at competitions and in the out-of-competition period and report to the ARAF any violations of the doping code by other athletes. Russia's indoor championships will take place in Moscow on Feb. 23-25.