It said the congress will be addressed by President Viktor Yushchenko, who is honorary chairman of the party.
Party Executive Committee Chairman Nikolai Katerynchuk said the congress will send a clear signal to society that the party is reforming itself and has a coherent strategy now that it has moved into opposition.
Ukraine's pro-presidential parliamentary bloc Our Ukraine officially announced Tuesday that it is switching to the opposition.
Relations between the bloc and the Russian-leaning government of Viktor Yanukovych, which came to power in August, have worsened as the government has dragged its feet on the president's key pro-Western policy goals. The bloc vowed October 5 to form a radical opposition, and called on its ministers to quit the Cabinet.
Ministers from the Our Ukraine bloc tendered their resignations Thursday.
The move signals an end to efforts at forming a grand coalition by President Viktor Yushchenko's six-party bloc and Prime Minister Viktor Yanukovych's pro-Russian Party of Regions and its allies, the Socialist and Communist parties.
After two months of talks, the two political factions still disagree on a series of crucial issues, including Yushchenko's drive to join NATO.
Our Ukraine said earlier it intends to form a shadow government.
The Our Ukraine bloc was part of the 'Orange' coalition, which emerged after the inconclusive March parliamentary elections, along with the Yulia Tymoshenko Bloc, which won 129 seats, and the Socialists.
The alliance collapsed when the Socialists defected to join the Party of Regions, led by President Viktor Yushchenko's former rival in the 2004 election and the current prime minister, Viktor Yanukovych, and the Communist Party, to form an 'anti-crisis' coalition.
Yanukovych said Tuesday he has agreed with President Yushchenko to continue working on a broad parliamentary coalition.
On Wednesday, however, President Yushchenko said his ministers have to be consistent and resign, abiding by the party's instructions.