South Korea's main opposition Democratic Party said Thursday it wishes to join forces with the splinter People's Party so the liberal bloc can grab a clear lead in the upcoming presidential election against conservative rivals.

"Experts say a change of the government can only be made through cooperation between the Democratic Party and People's Party," Rep. Woo Sang-ho, the floor leader of the main opposition party, said during the extra session at the National Assembly.

"We are not making the suggestion to deal a blow to the People's Party," Woo said, claiming if the two cannot merge together, they should at least start negotiations on establishing a joint government.

The People's Party spun off from the main opposition party last year, after the minor party's former head Rep. Ahn Cheol-soo had a falling out with Moon Jae-in, who currently stands as the most favored candidate in the polls.

As the splinter party holds a significant presence in progressive-leaning southwestern areas of the country, its support is still crucial for the Democratic Party.

Woo also said the party will seek to pass the bill on lowering the minimum voting age by a year to 18. 

The proposed change could influence the results of the presidential election, which would be held earlier than expected if the impeachment of President Park Geun-hye is confirmed by the Constitutional Court.

The party whip urged the Constitutional Court to come up with a fair ruling promptly, and claimed any result should be respected by both ruling and opposition parties.

As South Korea has 60 days to hold the presidential race if Park's ouster is approved, the election could take place after late April, if the top court makes the decision at end-February or early March. 

On the other hand, if the court rejects the impeachment motion, the general election will take place in December and the new president sworn into office in late February 2018.

Woo said controversial diplomatic issues, including the deployment of an advanced US missile defense system, should be discussed by the new administration.

The whip said the extra session should focus on ending behind-the-scenes ties among local family-controlled businesses, prosecutors and media, as such activities are cited for bringing about the alleged influence-peddling scandal surrounding Park. (Yonhap)