HARARE (Reuters) - Zimbabwe s ruling ZANU-PF is planning a special vote to give veteran President Robert Mugabe a fresh five-year mandate as party leader, three sources said, strengthening his hand as rivals plot to succeed him. One member of the party s politburo told Reuters the 93-year-old president could also use the party election in December to end divisions in its top ranks, raising the prospect of the removal of some of his challengers.  Comrade Mugabe is the only one center of power in ZANU-PF and that will be re-affirmed in December,  another politburo member told Reuters. Mugabe is the only leader Zimbabwe has known since its independence from Britain in 1980 and is due to stand again in presidential elections next year. But his age, rumors about his health and a mounting economic crisis have prompted open speculation in local media of factions competing for control of the party, one led by Mugabe s wife Grace. Politicians and diplomats told Reuters last month that Vice President Emmerson Mnangagwa had also been positioning himself for the day Mugabe either steps down or dies - an account backed up by hundreds of documents from inside Zimbabwe s Central Intelligence Organization. Leading members of the party held a five-hour meeting on Wednesday and decided to start making plans to hold the vote at a special congress, three people there said. Mugabe s term as party leader would have ended in 2019. A new mandate would take him past his 98th birthday.  His argument is that the party is divided and only an elective congress can unite the party and go into the elections as a united team,  the first politburo member said. When asked whether Mnangagwa would be fired at the meeting, the member said Mugabe was a stickler for party rules and had so far resisted pressure to ax the vice president outside such a congress. He did not elaborate further. Mnangagwa last week told reporters he had been poisoned in August - a report quickly dismissed by Grace Mugabe who went on to accuse the vice president of plotting to overthrow her husband. The vice president - also known as Ngwena or the Crocodile -was seen as Mugabe s favored heir when he was appointed in December 2014.  But his political fortunes have dimmed in recent months. On Monday, Mugabe stripped him of his control of the justice ministry in a reshuffle and fired three of his allies. 
Zimbabwe ruling party plans vote to strengthen Mugabe's hand