The ballot was originally scheduled for 2016 but has been repeatedly delayed, drawing accusations that Kabila, who has governed Congo since his father’s assassination in 2001, is trying to cling on to power.

Kabila denies that. But he has refused to rule out trying to change the constitution to remove term limits that bar him from standing for re-election.

Katumbi left Congo for South Africa in May 2016 for medical treatment after being accused by state prosecutors of hiring mercenaries, and has been courting African regional and international support for his efforts to press Kabila to stand down.

“I’m not scared of returning to Congo,” Katumbi told a news conference in Johannesburg after he launched Ensemble - meaning“Together” - a new opposition coalition.

“I will be there to present my candidacy,” he added, while declining to give a date and refusing to be drawn on whether he had won support from regional leaders.

Returning to Congo would expose Katumbi to arrest after he was sentenced in June 2016 to three years in prison for real estate fraud. He says the accusations against him are politically motivated.

Failure to hold the election in December could embolden militia groups whose attacks have forced many people to flee their homes, deepening a humanitarian crisis.

The unrest has caused fears that Congo, a vast, undeveloped country that sits in the heart of Africa, could slide back into civil war. Civil conflict killed millions in the country at the turn of the century.

Katumbi, who established his political credentials as the governor of the mineral-rich southwest province of Katanga, also had harsh words for Kabila’s signing into law on Friday of a new mining code that imposes big hikes in taxes and royalties.

If elected, Katumbi said he would sit down with mining companies and work towards a more equitable system of levies on the mining industry, one of Congo’s few sources of foreign exchange.

“If there’s no stability, even a dog can’t come and invest in the Congo because there’s no guarantee of the money,” he told Reuters on the sidelines of the Ensemble meeting.“We have to give respect to the investors.”