South Korea's two most popular opposition groups reached an agreement Friday on the next steps for their planned merger, paving the way for its launch ahead of upcoming local elections.

   The agreement came five days after the main opposition Democratic Party (DP) and the opposition group led by popular independent lawmaker Ahn Cheol-soo announced the merger in a surprise move that changed the political landscape ahead of the June 4 local elections.

   Public interest in the planned merger is especially high due to the potential challenge it could pose to the ruling Saenuri Party in the June 4 elections seen as a confidence vote on the incumbent government of President Park Geun-hye.

   Friday's agreement calls for a step-by-step process under which Ahn's group and a portion of the DP will first create a new party on their own and then have the rest of the DP join them.

   That method is seen as maximizing the benefits of the merger as it allows Ahn's group to play a leading role in the merger while the DP retains state funding.

   The agreement also calls for DP leader Kim Han-gil and Ahn to co-chair the future new party.

   The agreed method is largely in line with the demands of Ahn's group.

   Earlier in the day, the lawmaker called for reform and the setting aside of vested interests in remarks apparently aimed at the DP.

   "The key to success is whether we can show the public that we can reform and lay down our vested interests," he said during a forum. "If we can't demonstrate that, this venture will become difficult; if we can demonstrate that, the people will become the final victors."

   The DP leader stressed that sincerity will be the only "lubricant" for the two groups' merger.

   "Currently, we are in the process of determining the overarching principles of unification and negotiating as we work with what is realistically possible," he said at a meeting of the party's Supreme Council. (Yonhap)