KIEV, March 31 - Ukraine’s two largest opposition groups on Friday failed to agree on a major unification plan ahead of parliamentary elections in October, but pledged to do so before the end of April.

Arseniy Yatseniuk, a former Parliamentary speaker and the second most popular opposition figure, was expected to announce the decision that he lead jailed former Prime Minister Yulia Tymoshenko’s Batkivshchyna party.

Instead, he said the agreement should be reached within the next three weeks.

“I think we’re at the finish line,” Yatseniuk told members of the Batkivshchyna party at its emergency meeting on Friday. “Let me suggest that within three weeks we put a period in discussions of how the united opposition is to win.”

The opposition groups plan to defeat President Viktor Yanukovych’s Regions Party at the October election to start reversing what they believe policies undermining democracy in the country.

The unification of Batkivshchyna and Yatseniuk’s Front of Changes, currently the two most popular opposition groups in Ukraine, is thought to create a synergy needed for defeating the Regions Party.

“We have to drop the talk of running with several groups,” Tymoshenko, who services a seven-year jail sentence in the Kharkiv prison, wrote in her address to the meeting. “The unification of the opposition groups must give a powerful cumulative effect.”

“The only thing what the governing party is afraid of is the unification of the opposition,” she wrote. “That’s why is ask you of only one thing: unite!”

A half of the 450-seat Parliament will be elected in individual constituencies and a half on the party-list votes.

Yatseniuk said Friday that before he makes the decision, the opposition parties must agree on 225 single candidates running against pro-government candidates in individual constituencies at the elections.

Lawmakers said the plan calls for Yatseniuk to lead the united opposition group, based on the Batkivshchyna party, for the election.

Yatseniuk and his allies, according to the plan, would control 45% of seats, while Tymoshenko’s allies would control the majority of the group with 55% of seats.

Another bone of contention in the discussions between Yatseniuk and Tymoshenko’s allies, however, is who will be running against President Viktor Yanukovych in the March 2015 presidential election.

Oleksandr Turchynov and other senior members of the Batkivshchyna party, have been insisting it must be Tymoshenko, while Yatseniuk has maintained the single candidate to beat Yanukovych must be selected based on opinion polls, people familiar with the discussions said. (tl/ez)