The three estranged parties that had led the 2004 Orange Revolution against election fraud had been engaged in difficult talks to reunite, but their negotiations fell apart over the weekend.
Viktor Yushchenko's Our Ukraine party initially blamed the collapse on a disagreement with the Socialists over the parliamentary speaker's job, but later said the main disagreements were over policy.
Our Ukraine has said it is time to widen talks to include other parties, which could pave the way for an awkward alliance with Yushchenko's 2004 presidential election rival, Viktor Yanukovych, whose pro-Russian Party of Regions won the most votes in the March election. Tymoshenko's bloc came in second, winning more than Yushchenko's party and the Socialists combined, the AP reports.
Yanukovych's pro-Russian party said it was ready to hold talks with all the parties, and Our Ukraine appeared eager to start. The bitter falling-out between Yushchenko and Tymoshenko last year poisoned relations between their parties, and many analysts have said Yushchenko sees Yanukovych as a more reliable partner than Tymoshenko.