South Korea's main opposition party chief and a political heavyweight agreed Sunday to launch a new coalition party ahead of local elections in June, which are widely seen as a mid-term confidence vote for the Park Geun-hye administration.

Democratic Party leader Kim Han-gil and independent lawmaker Ahn Chul-soo said at a joint press conference that both sides agreed to form a unified political party as soon as possible to realize the transfer of power in the 2017 presidential election.

Ahn, who contested the 2012 presidential election as an independent candidate, dropped out of the race to support Democratic Party candidate Moon Jae-in. Moon was defeated by ruling Saenuri Party candidate Park Geun-hye by a narrow margin.

The businessman-turned-politician planned to launch his own New Political Vision Party, and decided to form a coalition with Kim to jointly fight against the Saenuri Party in the upcoming June 4 local elections.

The two political heavyweights also agreed to keep the 2012 presidential campaign pledge of abolishing the party nomination system for candidates in local elections.

The pledge to scrap the nomination system under which political parties put up candidates was made by both the ruling and opposition parties as well as Ahn in order to get rid of chronic political woe such as bribing the party into nomination.

In contrast to the ruling party deciding to keep the controversial nomination system, Ahn said Monday that his upcoming party will not nominate candidates for mayors and local councilors in the June 4 local elections.

Kim proposed Friday night to Ahn to form a new coalition party, saying that the Democratic Party will not adopt the party nomination system, resulting in the joint press conference Sunday morning.

The joint statement read by Kim and Ahn said that new politics will base on building trust with people by keeping promises.

The coalition party will pursue policy of economic democratization and welfare state, as well as peace on the Korean Peninsula.