Opposition parties from the Democratic Republic of Congo announced the formation of yet another coalition to oppose efforts by President Joseph Kabila to hold on to power. The ruling party responded by describing the action as an attempt to overthrow the government.

In a declaration, signed Friday after a meeting near Brussels, the opposition called for Kabila to step down at the end of his second term on Dec. 19. It said representatives from the international community should participate in talks between the opposition and the ruling party to ensure a transfer of political power this year.

“The opposition parties will remain united to ensure the struggle of the Congolese people to achieve a political change and ensure the rule of law succeeds,” according to the signed declaration, published via Twitter.

Kabila, who won elections in 2006 and 2011, is barred from running again by the constitution and is yet to publicly confirm he will step down. While elections are scheduled for November, the government and the electoral commission have said that logistical and financial constraints mean the poll is likely to be delayed. Last month, Congo’s Constitutional Court ruled that Kabila can stay in power if the vote isn’t held.

The ruling party attacked the opposition move at a press conference called hours after the Belgian declaration was made public. “The Presidential Majority rejects all of the resolutions adopted at this meeting as an attempted coup d’etat,” Secretary-General of the Presidential Majority Aubin Minaku told reporters in the capital, Kinshasa.

In November, the president for called for a national political dialogue to discuss the organization of elections. The talks haven’t taken place and a preparatory committee has yet to be appointed. Opposition leaders, who say Kabila is deliberately blocking the organization of the elections in order to hold on to power, have mostly rejected the dialogue, calling instead for negotiations to be organized by the international community.

The Africa Union in April appointed Edem Kodjo, the former Prime Minister of Togo, to facilitate the talks. On June 6, international partners including the United Nations, European Union and the Southern African Development Community said they had agreed to establish a panel to support discussions.

The opposition remains reluctant to participate unless other commitments are made, including that Kabila leave power on Dec. 19. That demand “violates the constitution,” Lambert Mende, minister of communications, said after Friday’s press conference. “The president can only be replaced by a president elected by the Congolese people.”

The meeting in Brussels is another attempt to unite Congo’s opposition, this time under the leadership of the long-time opposition leader Etienne Tshisekedi. While former provincial governor Moise Katumbi, who is receiving medical treatment in London, didn’t attend themeeting, the G7 group, which named him in March as their presidential candidate, was present and signed the declaration.