The Democratic Republic of Congo's opposition parties agreed on Thursday to name a single unity candidate by mid-November to run against President Joseph Kabila's choice in December elections.Tensions are running high before the long-delayed December 23 vote to chose a successor to Kabila, who bowed to international pressure this year to step aside after nearly two decades in power.In a statement after two days of talks in Johannesburg, the country's fragmented opposition parties said they would "decide to appoint a common candidate" before their next meeting no later than November 15.Key opposition candidates Martin Fayulu, Vital Kamerhe and Freddy Matungulu participated in the meeting. Felix Tshisekedi, from the main UDPS opposition party, sent a delegate as did the two heavyweight contenders excluded from the election race - former warlord Jean-Pierre Bemba and regional baron Moise Katumbi.Western powers are watching DRC election developments closely as the huge, mineral-rich African state attempts its first peaceful transition of power since independence from colonial Belgium in 1960.Kabila last month promised at the United Nations the country would hold a credible ballot. But the months before he said he would step aside were marred by brutally repressed protests.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and FacebookCritics worry Kabila is trying to make sure his favoured successor, Emmanuel Ramazani Shadary, a hardline former interior minister, faces no serious challenger.The use of South Korean-made voting machines has become a point of contention. Critics say they will allow ballot-rigging; authorities say they will cut costs and prevent fraud.The opposition reasserted its decision not to boycott the election and demanded electoral authorities guarantee a "free, credible and inclusive" ballot.The statement also called for the withdrawal of the voting machines, because it said using touch screens to print bulletins in the polling stations could permit fraud.Opposition parties plan a rally on Friday in the capital Kinshasa to demand the voting machines be withdrawn.Kabila, 47, has been in power since 2001. His second and final elected term in office ended nearly two years ago, but he stayed in office thanks to a caretaker clause in the constitution.