Kinshasa - Democratic Republic of Congo's main opposition party said on Monday it would join a march backed by the country's powerful Catholic Church on February 25 to demand President Joseph Kabila's resignation.In a statement, the Union for Democracy and Social Progress (UDPS) said a party congress scheduled for February 26-27 "is being postponed to support the march on February 25.""All activists are urged to respond massively," it said.Kabila, 46, took over from his assassinated father in 2001. His regime, widely criticised for corruption, repression and incompetence, faces mounting protests over his refusal to leave office after his term expired in December 2016.The church brokered an accord under which Kabila could remain in power provided new elections were held in 2017 - a deal that fell through after the electoral authorities said it needed more time to compile a voters' register.KEEP UPDATED on the latest news from around the continent by subscribing to our FREE newsletter, Hello Africa.FOLLOW News24 Africa on Twitter and Facebook. It wants him to pledge to stand aside in the presidential vote set for December 23 this year, and to respect fundamental freedom.An organisation closely associated with the Catholic Church, the Lay Coordination Committee (CLC), announcing the February 25 march date on Saturday, called on the public "regardless of religious or political affiliation... to say no to dictatorship.""Let us be ready to face the worst in order to triumph in the best," it said.Church leaders have escalated a rhetorical campaign against Kabila and thrown their weight behind two previous marches, on December 31, 2017, and January 21, that were brutally repressed. Fifteen people were killed in the two protests, according to UN and Church figures. The authorities say two people were killed. The Democratic Republic of Congo's National Human Rights Commission lists seven dead in the New Year's Eve protest, and four on January 21.The UDPS is holding a congress to elect a successor to its veteran leader, Etienne Tshisekedi, who died in Brussels on February 1, 2017. The repatriation of his body has in itself become a source of political tensions.