She suggested a credible vote will also help Congo alleviate its humanitarian crisis, attract foreign investment, and stabilize central Africa.
The elections were originally due to take place in 2016, but were delayed as President Joseph Kabila refused to leave office at the end of his mandate.
Congolese authorities have blocked several opposition leaders from running for president, most prominently former vice president Jean-Pierre Bemba.
Opposition parties agreed to unite behind a single candidate for the election, businessman Martin Fayulu. But two opposition leaders, Felix Tshisekedi and Vital Kamerhe, have since pulled out of the agreement.