WASHINGTON (Reuters) - The Democratic Republic of Congo s electoral commission is expected to announce in the coming days that a vote to replace President Joseph Kabila cannot take place until the end of 2018 at the earliest, people familiar with the process said. If confirmed, the decision could anger Congo s political opposition, which had struck a deal with Kabila for a ballot by the end of 2017. Kabila s refusal to step down at the end of his second elected term in December 2016 sparked protests that killed dozens of people and raised fears that the chronically unstable country could slide back into civil war. Term limits preclude him from running again. The independent commission believes it cannot complete preparations to ensure a secure, transparent election until December 2018, said the two sources from Congo, who spoke to Reuters in Washington on condition of anonymity ahead of an official announcement. Even that 2018 date presumes that there will be significant domestic and international support for the election, which is expected to cost $526 million to carry out, excluding expenses for registering voters. Without sufficient support, preparations for the election could take even longer, pushing the vote to May or July of 2019, the first source said. One of the big challenges is a lack of trust within Congo about the political process itself, the sources said. Securing international support for the new date will also be vital, since a global backlash could trigger more infighting in Congo.  There is mistrust between actors, especially political actors,  the first source said.  No one trusts nobody. And this mistrust is ... also even toward the electoral process.   For example, any U.S. decision to contest the new date could  put in motion contestations of the calendar and delay, again, the elections,  the second source said.  Government spokesman Lambert Mende said the electoral commission was independent of the administration and had sole responsibility for setting the election calendar. The stakes are high. Resource-rich Congo, which gained independence from colonial power Belgium in 1960, has never had a peaceful transition of power. Kabila s opponents have long suspected he intends to repeatedly delay elections until he can organize a referendum to let himself stand for a third term, as his counterparts in the neighboring Congo Republic and Rwanda have done. Kabila denies those accusations, saying the election delays stemmed from budgetary constraints and the challenge of registering millions of voters. Congo is moving toward  credible, transparent and peaceful elections,  he told the United Nations last month. The first source also cited several hurdles to preparing for the next election, including completing a $400 million effort to register Congo s 45 million voters and ensure that none of them can cast more than one ballot. Some 42 million people have been registered so far. Once registration is complete, Congo s parliament must approve a law on distribution of parliamentary seats that will also be up for election. Then the country s hundreds of political parties need to nominate candidates for the posts, the first source said. As a result, voters are likely to have to choose from tens of thousands of candidates for hundreds of parliamentary and provincial government seats on the presidential ballot.  Millions of newspaper-sized packets of ballot paper need to be printed, probably in China or South Africa, and distributed, the sources said. Congo will need logistics support as well, including leased aircraft from the United Nations. The nation must also guarantee security for voters, which is no small task.  In the central Congo Kasai provinces, an insurrection by the Kamuina Nsapu militia, which demands the withdrawal of Congolese forces from the area, has driven 1.4 million people from their homes and killed more than 3,000 since August 2016. A rebel spokesman in eastern Congo said on Sept. 29 that his forces intended to march across the country to the capital Kinshasa to depose Kabila.      No security, no election in that area,  the first source said. U.S. President Donald Trump said last month that the United States was deeply disturbed by violence in South Sudan and Democratic Republic of Congo and that he would send U.N. Ambassador Nikki Haley to Africa to discuss conflict prevention.     Kabila took power in 2001 after the assassination of his father, Laurent Kabila, an ex-rebel who had forced out President Mobutu Sese Seko. Joseph Kabila won elections in 2006 and 2011, but both were marred by violence. People are also restless over the state of the economy. Although it has big reserves of gold, cobalt, diamonds, tin and coltan, which is used in laptops and mobile phones, the vast country has been hit by the fall in global commodity prices. 